Is there a risk of inbred children with fake fatherhood?

Solution 1:

No, it shouldn't. In case of bastards, the game records the real fatherhood behind the curtain, and calculates the risk of inbreeding by the genetic family ties.

Example character:

        birth_name="Aghsartan"
        birth_date="1214.2.3"
        father=582283
        real_father=568231
        mother=583069

That also means, that you can inadvertently commit incest, when the real paternity of the characters are unknown to the characters.

If you want to avoid this, you can turn extra character info on, by typing charinfo on in the console. The character tooltips will now show you some hidden info, such as their health pool, ethnicity, fertility, biological father and more.

Solution 2:

The game mechanics have an internal awareness of who the actual father was, this enables in game events to be triggered such as:

• "I am a bastard"
• "The father's wife is angered"

and my personal favourite:

• "I'm not your son. I'm your brother"

So IF the father is of a different family and you marry him off to a relative then there will be no risk of inbreeding.

That is IF the father is of a different family and that is a big IF, the real father will likely be someone in your court which could include your sons, brothers etc etc.

Solution 3:

It'd be based on their biological father (probably the other guy).

A character's real father is recorded in their stats. This is not normally displayed, but is visible in non-ironman save files or by entering charinfo into the console.

This means that you can safely marry your son to other dynasty members. On the other hand, you probably shouldn't marry him to anyone who might be his half-sister.

Bear in mind that the "but wasn't I away" event can happen with legitimate children, especially if you are paranoid. The child might actually be yours.