I know that inbreeding within a family can cause the characters to have bad traits so that the descendants can get mad or something like this.
But is it also possible to inbreed with another family? That is: If I am, for example, Byzantium and I always marry my heir off to Hungarian princesses, will this lead to the effects inbreeding has when done within the family?
Best Answer
I realize this question is over 2 years old, but I went ahead and did some digging. It appears that the answer, oddly, is no. The "Inbred" hidden statistic (which governs the Inbred traits) is not generated through marriage; instead, a new character has a 1% chance of gaining one point on coming of age. If their father has any Inbred points, this increases to 50%, with an additional 25% chance to gain a second point. I wasn't able to decipher all the data I found, but intuitively I would expect that each further level of Inbred which your father has (up to 6!) increases the odds that his children will gain more Inbred points.
You can see more at this Gamefaqs guide, which is very comprehensive.