血亲圣婚 是某些宗教的特色， 允许并鼓励角色跟近亲结婚
最初有两个宗教允许血亲圣婚：
琐罗亚斯德教 
和祷告派 
(聂斯脫里派的异端)
同时也可以在改革原始宗教时作为
教义而被选择。
血亲圣婚的好处
血亲圣婚时，统治者会获得虔诚：一般的是50、公爵是100，国王是200、皇帝是300，并可以赚取类似数量的威望或金钱。
并会有一些永久性好感修正：
| 好感修正 | 类别 | 宗教 | 对象 | 数值 |
|---|---|---|---|---|
| 血亲圣婚 | 封臣 | (有圣婚的宗教) | 封臣 | +5 |
| 血亲圣婚 | 牧师封臣 | (有圣婚的宗教) | 封臣 | +15 |
| 亵渎婚姻 | 封臣 | (无圣婚的宗教) | 封臣 | -10 |
Strategies
Positive genetic traits
If using Ruler Designer, consider giving your starting ruler the positive genetic traits 
or 
, 
and 
. This does not reduce the risk of 
, but does improve the pool of potential spouses for your heir.
Mitigating the risk of inbreeding
Zoroastrians who choose to partake in divine marriages are at high risk of inbreeding. The risk of your dynasty dying out due to bad congenital traits (characters being inapt to rule, having fewer children and dying younger) is quite serious after a few generations. To prevent this you may:
- Prefer half-siblings (0.25) to full siblings (0.5) or offspring (0.5)
- Take concubines to produce heirs with more genetic diversity
- Marry dynasty members past child-bearing age
- Land dynasty members frequently to increase the pool of characters you can marry in the long term (unlanded characters are limited on number of children)
- Skip inept heirs, e.g. using feudal elective succession