I got an event where my wife cheated on me and got pregnant, but I was unable to prove it. Now her son is listed as my legitimate son. We appear as father and son in family trees, relationship screens etc., even though his actual biological father is definitely someone else.
When I marry him to a close relative from my side of the family, is there a risk that their children will turn inbred? Common sense would say "no", but it seems like the game treats me as the biological father for all intents and purposes, so I have my doubts.