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At least some were last verified for version 1.10.
A diagram showing family relations in Crusader Kings III
The Family of a character consists of their relatives, both closer and more distant. A character's grandparents, parents, siblings (including half-siblings), children and grandchildren are considered Close Family while uncles, aunts, first cousins, nephews and nieces are considered Extended Family. More often than not, most family members belong to the same Dynasty.
A character will gain 
Stress if a parent or sibling dies before the age of 65.
Contents
- 1 Marriage
- 1.1 Polygamy
- 1.2 Marriage acceptance
- 2 Incest
- 3 Trait inheritance
- 3.1 Active and inactive traits
- 3.1.1 Chance of active inheritance
- 3.1.2 Chance of inactive inheritance
- 3.2 General logic for trait with tiers inheritance
- 3.3 List of congenital traits
- 3.3.1 List of other inherited traits
- 3.1 Active and inactive traits
- 4 Inbreeding
- 4.1 Chance of inbreeding
- 4.1.1 Common ancestors
- 4.1.2 Inbreeding factor
- 4.1.3 Effect of Pure-blooded on inbreeding
- 4.2 Traits gained from inbreeding
- 4.2.1 Inbred
- 4.2.2 Pure-blooded
- 4.1 Chance of inbreeding
- 5 References
Marriage[edit | edit source]
Marriage is the legal union between two characters in a personal relationship. Only characters who are at least 16 years old may marry, and they require to be of the opposite gender unless the Same-Sex Marriages game rule has been changed to Accepted. If either character is 15 years old or younger, the two prospective partners may enter a betrothal instead until both parties come of age.
Spouses, concubines, and consorts who are fertile are able to have legitimate children. Children in a marriage belong to the father's house unless the marriage is Matrilineal, in which case they belong to the mother's house. Moreover, marriage is one of the two main ways to form an 
Alliance with other characters.
A faith's doctrines affects who a character may marry, how many official partners they may have and whether marriage may be ended in divorce:
The Consorts & Concubines marriage type doctrine allows rulers to have up to three consorts or concubines, alongside their spouse. Children born of consorts or concubines gain the Child of Consort/Concubine trait. Unlike marriage, concubinage does not yield alliances; however, consorts and concubines can be set aside at will without the need for divorce.- Consanguinity doctrine determines the legality of incestuous marriage.
- Marriage may be ended subject to divorce doctrine. The target of the divorce gains −25 Opinion (Divorced Me) for 50 years with their ex-spouse, while their close family members gain −5 Opinion (Divorced Close Family) for 5 years. Divorced characters may remarry.
- Certain cultural Traditions can override the above faith doctrines: the Monogamous/Polygamous/Concubines traditions sets marriage type, while Marital Ceremonies blocks divorcing.
The Consorts & Concubines marriage type doctrine allows rulers to have up to three consorts or concubines, alongside their spouse. Children born of consorts or concubines gain the 
Marriage may be ended subject to Having a lover outside of marriage creates a 
Lover secret. If it is revealed, it may result in the two lover characters gaining the 
Fornicator and 
Adulterer traits, depending on the faith's 
/ 
adultery doctrines. Children known to be born out of wedlock gain 
Bastard (trait), or 
Wild Oat if their faith has the 
No Bastards bastardry doctrine. If a bastard successfully becomes landed, they gain the 
Bastard founder trait.
Polygamy[edit | edit source]
| Title tier | Expected spouses |
|---|---|
 Unlanded | 1 |
 Baron | 1 |
 Count | 1 |
 Duke | 2 |
 King | 3 |
 Emperor | 4 |
With the Polygamous marriage type doctrine, characters may marry one spouse, and rulers (depending on their View on Gender doctrine) may additionally have up to three secondary spouses. If two married rulers have the Polygamous doctrine and are allowed to do so by the gender doctrine, they may have multiple spouses each. With the Equal gender doctrine, there is no existing restriction on having the same spouse(s) as another ruler.
Any spouse who follows a Faith that has the Monogamous doctrine will suffer −40 
Opinion. Monogamous spouses who were previously in a polygamous marriage (e.g. a secondary spouse was divorced) will still suffer −20 Opinion for 20 years. Any monogamous close relatives will suffer a similar −20 Opinion modifier. Spouses with the Consorts & Concubines doctrine or Polyamory tenet do not suffer similar penalties. When arranging marriages, prospective spouses who would become part of a polygamous marriage and do not believe in polygamy suffer a marriage acceptance penalty of .
Rulers receive a penalty of 
−0.5 monthly piety per missing spouse if they are under the expected spouse amount for their title tier:[1]
Marriage acceptance[edit | edit source]
In order to successfully arrange marriages with AI characters, the player must reach a marriage acceptance score of at least +1 for the prospective spouses. Below is a list containing all possible conditions that affect marriage acceptance:[2]
| Condition | Marriage acceptance |
|---|---|
| Weak hook | +100 |
| Strong hook | +200, or auto-accept |
| Promising Prospects Perk |
|
| Dynasty Glory Perk | +30 |
| Arranging own marriage | −15 |
| Is player's heir |
|
| Desires alliance | Varied |
| Does not want alliance | −100 |
| Marrying up | +30 for each difference in title rank |
| Marrying down |
|
| Opinion |
|
| Wishes well for Lovers | +15 |
| Prospective spouses love each other and AI has compassion greater than zero | +0.25 per AI compassion |
| Candidate is Lowborn |
|
| Candidate's Level of Splendor | +(Level of Splendor * 5 - 5) |
| Incorrect marriage (patrilineal/matrilineal) | Varied |
| Isolationist tradition towards other cultures |
|
| Marital Ceremonies |
|
| Different faith |
|
| Faith does not have polygamy doctrine or polyamory tenet and potential spouse would belong in a polygamous marriage. | −1000 |
| Age Considerations | Varied |
| The marriage will have Low Fertility | Varied |
| Unimportant courtier | +10 |
| Important courtier | −10 |
| Prospective spouse is a parent of recipient's children | −25 |
| Player is AI's liege |
|
| Valuable claimant | −50 |
| Claimant to one of AI's titles | −50 |
| Intimidated | Varied |
| Terrified | Varied |
| Character is dear to AI | Varied |
| The marriage would be incestuous | −1000 |
| Age of recipient | +(Recipient age − 20) |
| Spouse councillor - boosted child or heir |
|
Incest[edit | edit source]
Incest is sexual activity between family members. A faith's 
Consanguinity doctrine determines the legality of incestuous marriage. Characters having an incestuous relation that would not be allowed in marriage gain the Is Incestuous secret, and if exposed the 
Incestuous trait. Any form of incestuous relation, legal or not, may risk producing inbred offspring.
The Divine Marriage tenet provides bonuses to incestuous marriages.
Relatives are harder to seduce unless the target character's Faith accepts such an incestuous relation or the seducer has the Subtle Desire perk (
Seducer tree).
Trait inheritance[edit | edit source]
Congenital traits can be inherited by a character's offspring. Although congenital traits must be visible (active) to provide stat bonuses and other effects, a character may also carry recessive (inactive) traits which are invisible, yet can still be inherited by one's children.[3]
There are some traits that are inherited by children, but do not use the active/inactive inheritance mechanic. In the context of this section, the term congenital trait excludes such traits. It also does not include traits that are non-genetic, yet inheritable.
Trait inheritance mechanics also apply to children generated after creating a custom ruler.
Active and inactive traits[edit | edit source]
A congenital trait may be either active or inactive; active traits are visible and provide effects, whereas inactive traits are hidden. The genetic versions of 
Melancholic, 
Lunatic and 
Possessed are always inherited inactively and become active later in life:[4]
| Trait | Activation time (after birth) | |
|---|---|---|
| Days | Years[5] | |
| Melancholic | 3,650-5,000 | Between 10 years and 13 years, 9 months, 12 days |
| Lunatic | 5,840-10,950 | Between 16 years and 30 years |
| Possessed | 3,650-7,300 | Between 10 years and 20 years |
Chance of active inheritance[edit | edit source]
The chances of inheriting a congenital trait as an active trait is based on what version (active or inactive) the parents have:[6]
Mother Father | None | Inactive | Active |
|---|---|---|---|
| None | 0% | 2% | 25% |
| Inactive | 2% | 10% | 50% |
| Active | 25% | 50% | 80% |
Chance of inactive inheritance[edit | edit source]
If the child does not inherit actively, there is a chance that they will inherit the trait as an inactive trait instead:[6]
Mother Father | None | Inactive | Active |
|---|---|---|---|
| None | 0% | 25% | 75% |
| Inactive | 25% | 50% | 100% |
| Active | 75% | 100% | 150% |
General logic for trait with tiers inheritance[edit | edit source]
- Start from highest trait
- Calculate active chance. Lower tiers ( including inactive ) count as inactive of the tier. Each level down beyond the first multiplies chance by a define
- If active, use it; DONE
- Otherwise, go down a tier, if inactive pretend 1 more parent has that tier active, otherwise 1 more parent has it inactive.GOTO 2
When trying to inherit a tiered genetic trait, and the other person has one of lower tier, we pretend that means they've got the higher tier one recessively, and reduce the chance of inheritance by 20% per tier further down than 1 the other parent's trait is.
When going down a tier, add 40%.[6]
List of congenital traits[edit | edit source]
The table below contains all genetic traits that use the inheritance mechanism as described above.[7][8] This list does not contain traits such as 
Sayyid, which can be inherited from a character's non-biological parent (in the case of secret bastards), or 
Inbred which uses a custom inheritance chance. The natural prevalence column denotes the likelihood of any character being born with the trait if it is not inherited from their parents. For every trait with natural prevalence, the same value can be assumed for random prevalence (i.e. for generated characters).[7] Note that some traits cannot be inherited at the same time since they are incompatible; such traits are indicated if they belong in the same group.
| Trait | Natural prevalence (%) | Group | Notes |
|---|---|---|---|
| Melancholic (genetic variant) | 0.5 | - | If inherited on birth, it is initially hidden.[9] |
| Lunatic (genetic variant) | 0.5 | - | If inherited on birth, it is initially hidden. |
| Possessed (genetic variant) | 0.5 | - | If inherited on birth, it is initially hidden. |
 Homely | 0.5 | Beauty | |
 Ugly | 0.25 | Beauty | |
 Hideous | 0.15 | Beauty | |
 Comely | 0.5 | Beauty | |
 Pretty / Handsome | 0.25 | Beauty | |
 Beautiful | 0.15 | Beauty | |
 Slow | 0.5 | Intelligence | |
 Stupid | 0.25 | Intelligence | |
 Imbecile | 0.05 | Intelligence | |
 Quick | 0.5 | Intelligence | |
 Intelligent | 0.25 | Intelligence | |
 Genius | 0.05 | Intelligence | |
 Delicate | 0.5 | Physique | |
 Frail | 0.25 | Physique | |
 Feeble | 0.15 | Physique | |
 Hale | 0.5 | Physique | |
 Robust | 0.25 | Physique | |
 Amazonian / Herculean | 0.15 | Physique | |
 Fecund | 0 at birth[10], unknown for generation | Fertility | |
 Club-footed | 0.5 | - | Also gained via inbreeding. |
 Hunchbacked | 0.5 | - | Also gained via inbreeding. |
 Lisping | 0.5 | - | |
 Stuttering | 0.5 | - | |
 Dwarf | 0.5 | Stature | Also gained via inbreeding. |
 Giant | 0.5 | Stature | Also gained via inbreeding. |
 Spindly | 0.5 | Physique (incompatible with good traits) | Also gained via inbreeding. |
 Scaly | 0.5 | - | Also gained via inbreeding. |
 Albino | 0.5 | - | |
 Wheezing | 0.5 | - | Also gained via inbreeding. |
 Bleeder | 0.5 | - | Also gained via inbreeding. |
 Barren / Sterile | 0.5 | Fertility | Also gained via inbreeding. |
List of other inherited traits[edit | edit source]
- See also: Descendant traits
The following list contains all other traits that use a separate inheritance mechanic. For entries without a chance to inherit value for both parents, assume the value for single parent.
| Trait | Chance to inherit (%) | Notes | |
|---|---|---|---|
| Single parent | Both parents | ||
 Great Pox | 10 | - | |
 Lover's Pox | 10 | - | |
 Pure-blooded | 15 | 75 | Gained initially through inbreeding. |
| Inbred | 15 | - | Gained initially through inbreeding. |
| Sayyid | 100 | - | Only inherited from apparent father. |
 Saoshyant /  Saoshyant Descendant | 100 | - | When parent has Saoshyant, Saoshyant Descendant is inherited instead.[11] |
 Paragon /  Consecrated Blood | 100 | - | When parent has Paragon, Consecrated Blood is inherited instead. |
| The Savior / Divine Blood | 100 | - | When parent has The Savior, Divine Blood is inherited instead. |
Inbreeding[edit | edit source]
Inbreeding is the process of two related characters having children together. For these purposes, related characters are those who share a common ancestor. Such children can be born with negative congenital traits even if neither parent has them, or the Inbred trait in advanced cases. However, there is a small chance for the child to gain the Pure-blooded trait instead.
In the first generation, small-scale incest such as cousin marriage may not have a massive immediate impact. Nonetheless, repeated instances over successive generations may have an accumulative effect through negative inherited traits and a narrowed gene pool.
Chance of inbreeding[edit | edit source]
A line graph showing chance of inbreeding based on common ancestors.
The chance of a child being considered inbred can be found from the product of the following:[12]
- Number of common ancestors
- Inbreeding factor based on number of common ancestors
- Inbreeding chance modifier. Currently, only the Pure-blooded trait provides such an effect.
Common ancestors[edit | edit source]
The more common ancestors two parents have within four generations (up to their great-great grandparents, and including themselves), the more likely their children will be inbred.[13] Some potential incestuous marriages are noted below. The value provided for common ancestors assumes that ancestors were otherwise non-incestuous and monogamous. Cousins are not removed. The term "nibling" refers to niece/nephew. Additionally, the value is relative to the breeding couple.
| Relation | Common ancestors | Explanation |
|---|---|---|
| Full siblings | 30 (maximum possible) | By definition, (full) siblings share parents, and thus by extension all other ancestors. The maximum amount of shared ancestors from n generations can be found from  , thus being 30 from 4 generations. Or, written out, full siblings share both parents (2), two sets of grandparents (4), four sets of great grandparents (8) and eight sets of great-great grandparents (16). |
| Parent-child | 15 | In the case of a partner being the other partner's ancestor, they are counted as a common ancestor.[14] As a result, the common ancestors are the following (perspective is child/parent): parent/self (1), one set of grandparents/both parents (2), two sets of great-grandparents/standard grandparents (4), four sets of great-great grandparents/great grandparents (8). Note that the parent's great-great grandparents are the child's 3×-great grandparents, and are therefore not counted. |
| Half siblings | 15 | They share one parent, and therefore share only half of the maximum amount of ancestors. Alternatively, they share one parent (1), one set of grandparents (2), two sets of great grandparents (4) and four sets of great-great grandparents (8). |
| First cousins | 14 | First cousins share grandparents (2), two sets of great grandparents (4) and four sets of great-great grandparents (8). |
| Uncle-niece/aunt-nephew | 14 | Similar to first cousins, but rather than sharing grandparents, the nibling's grandparents are the uncle/aunt's parents. Note that since the uncle/aunt's great-great grandparents are the nibling’s 3×-great grandparents, who are 5 generations away from the nibling’s perspective, they are not counted. |
| Second cousins | 6 | Second cousins share one set of great grandparents (2) and two sets of great-great grandparents (4). |
| Third cousins | 2 | Third cousins share one set of great-great grandparents. |
Inbreeding factor[edit | edit source]
The inbreeding factor for a given amount of common ancestors can be found through the following:[6]
| Common ancestors | Factor | Chance before modifiers |
|---|---|---|
| 0-14 | 0.33 | Between 0% and 4.62% |
| 15-16 | 0.75 | Between 11.25% and 12% |
| 17-19 | 1 | Between 17% and 19% |
| 20-21 | 2 | Between 40% and 42% |
| 22-30 | 3 | Between 66% and 90% |
Effect of Pure-blooded on inbreeding[edit | edit source]
The Pure-blooded trait provides −50% chance of inbreeding per parent. If two parents have the Pure-blooded trait, this effect combines to no chance of gaining traits due to inbreeding. Note that this excepts the chance of gaining the Pure-blooded trait naturally, as well as the inheritance of such traits via parents. It is unknown whether the Pure-blooded trait has an effect on gaining the Inbred trait.[9]
Traits gained from inbreeding[edit | edit source]
The following traits may be gained from inbreeding. Note that these general inbred traits may also be gained naturally and are congenital. Offspring only have a chance to gain these traits as a result of inbreeding if their parents do not possess any of these traits (plus the Inbred trait).[15] The traits below appear equally likely.[9]
- Barren / Sterile
- Scaly
- Club-footed
- Wheezing
- Spindly
- Giant
- Hunchbacked
- Bleeder
- Dwarf
Additionally, there are two traits that may only be gained initially through inbreeding and have special requirements: Inbred and Pure-blooded.
Inbred[edit | edit source]
The Inbred trait may be inherited from one's parents. It may also be gained if a character with a general inbred trait has children with someone with whom they share a common ancestor.[15] The chance of gaining the Inbred trait as a result of this is unknown. Note that even with highly incestuous marriages, no children will gain the Inbred trait if the parents do not possess any of the enabling traits.[9]
Pure-blooded[edit | edit source]
The Pure-blooded trait may be inherited from one's parents. Otherwise, it may be gained naturally. Similar to the chance of inbreeding, the chance of gaining the Pure-blooded trait naturally is based on the number of common ancestors, multiplied by the corresponding level factor for that amount of common ancestors:[6]
The inbreeding traits overwrite the Pure-blooded trait, thus the chance for a child to have the Pure-blooded trait by gaining it naturally is equal to the chance of not getting an inbreeding trait multiplied by the chance to get the Pure-blooded trait. This chance is maximized at 22 common ancestors for a value of 2.24%.
| Common ancestors | Factor | Final chance | Chance after Inbred roll |
|---|---|---|---|
| 0-19 | 0 | 0% | 0% |
| 20-21 | 0.15 | Between 3% and 3.15% | Between 1.8% and 1.83% |
| 22-30 | 0.3 | Between 6.6% and 9% | Between 2.24% and 0.9% |
As a result, parents must have at least 20 common ancestors for a child to gain the Pure-blooded trait naturally. This does not apply to inheriting it from parents.
References[edit | edit source]
- ↑
game\common\defines\00_defines.txt,PIETY_LOSS_PER_MISSING_SPOUSE = 0.5,DESIRED_SPOUSES_PER_TIER = { 1 1 1 2 3 4 } - ↑
game\common\scripted_modifiers\00_marriage_scripted_modifiers.txt,marriage_ai_accept_modifier - ↑ "[Genetic traits are] visible, though characters can also carry recessive traits... those are not visible, but can be inherited by their offspring!" rageair's reply in CK3 Dev Diary #7 - Characters & Portraits thread
- ↑
game\events\trait_specific_events\trait_specific_events.txt,trait_specific.0500 - ↑ All years in Crusader Kings III last 365 days.
- ↑ 6.0 6.1 6.2 6.3 6.4
common\defines\00_defines.txt,NChildbirth - ↑ 7.0 7.1
common\traits\00_traits.txt - ↑ "[If genetic = yes, the trait's] inheritance will follow the following rules: The trait can be inactive. Children can inherit the trait from both active and inactive parent traits. [...] An active trait is inherited with 100% chance, an inactive trait with a 50% chance. If the trait is successfully inherited from both parents, it becomes active. [...] If it's inherited only from one parent, it's inactive." Developer comments in
common\traits\_traits.info - ↑ 9.0 9.1 9.2 9.3 Pure-blooded effect on inbreeding on talk page
- ↑ Natural prevalence of Fecund on talk page
- ↑
events\decisions_events\major_decisions_events.txt,major_decisions.0101 - ↑ "The final chance [for inbreeding] in percent is given by the number of common ancestors X corresponding level factor X inbreeding chance modifier" Developer comments in
game\common\defines\00_defines.txt. - ↑
game\common\defines\00_defines.txt,NChildbirth|INBREEDING_ANCESTOR_GENERATIONS = 4 - ↑ The fact that the parents themselves are included in the common ancestor count is implied in the wording of developer comments found at
game\common\defines\00_defines.txt(emphasis added): "How many generations are checked for common ancestors of the both parents (including the parents) for the purposes of getting the inbreeding trait and the pure-blooded trait" - ↑ 15.0 15.1 "[enables_inbred = yes] enables the children of the character to be considered for the inbred trait (no by default). It only enables the inbred chance if there are common ancestors of the parents, so there is no risk of 'inbred' if the parents are not related. If inbred is not enabled by parents' traits, but there are common ancestors, there's a chance (same as for inbred trait when it's enabled) the child will get a random trait with enables_inbred = yes." Developer comments in
game\common\traits\_traits.info
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Greetings, fellow Crusader Kings III enthusiasts! As someone deeply immersed in the intricate dynamics of medieval nobility and familial ties within the game, I bring a wealth of expertise to shed light on the concepts outlined in the provided article.
Let's start with the core theme: Family Relations and Stress: The family structure in Crusader Kings III is crucial, encompassing Close Family (grandparents, parents, siblings, children, and grandchildren) and Extended Family (uncles, aunts, first cousins, nephews, and nieces). Stress can afflict a character if a parent or sibling dies before the age of 65, highlighting the emotional impact of familial loss.
Marriage and Alliances: Marriage serves as the legal union between characters, a key aspect of personal relationships. The age requirement is 16, and marriage is typically opposite-gender unless modified by the Same-Sex Marriages game rule. Marriage can yield legitimate children, forming alliances, and the faith's doctrines influence marriage dynamics, allowing rulers to have multiple consorts or concubines.
Polygamy: The Polygamous marriage type doctrine introduces the possibility of characters having multiple spouses, with the number depending on their title tier. Monogamous spouses may disapprove, leading to Opinion penalties.
Marriage Acceptance: Successfully arranging marriages with AI characters involves achieving a positive marriage acceptance score. Various factors influence this, including hooks, dynasty glory, opinion, alliances, faith, age considerations, and more.
Incest: Incestuous relations are determined by the Consanguinity doctrine of a faith. Incest may lead to the Is Incestuous secret and, if exposed, the Incestuous trait. The Divine Marriage tenet provides bonuses to incestuous marriages.
Trait Inheritance: Congenital traits, whether active or inactive, can be inherited. The chances of active or inactive inheritance depend on the parents' traits, with certain traits becoming active later in life.
List of Congenital Traits: The game includes an array of genetic traits, such as Melancholic, Lunatic, Homely, Intelligent, and others. These traits impact characters' stats and behaviors, contributing to the complexity of the game.
Inbreeding: Inbreeding involves characters with common ancestors having children. The chance of inbreeding is influenced by the number of common ancestors, the inbreeding factor, and the presence of the Pure-blooded trait, which reduces the chance of inbreeding.
Traits Gained from Inbreeding: Inbreeding can result in various traits, including Barren, Scaly, Club-footed, and the infamous Inbred trait. The Pure-blooded trait, obtained through inbreeding, mitigates the risk of negative traits.
This comprehensive overview provides a glimpse into the nuanced mechanics of Crusader Kings III, where strategic marriages, familial relationships, and genetic traits play pivotal roles in shaping the destiny of dynasties. If there are specific aspects you'd like further clarification on or if you seek guidance on specific strategies, feel free to inquire!
