That's why if you have incest scenarios where someone meets up with a long lost family member, it doesn't have the same kind of taboo meaning. Because how can you feel the same way, about someone you've just met or barely know? That person is effectively no different to any other stranger you might meet up with.
Well, actually here you have an indication of why I had made the incest patch for myself, and then kept making it also for others.
Is it a taboo, meaning with possible risks ? Yes.
Will they feel the same level of "feeling wrong or forbidden" ? No, at least unless they are made aware beforehand of the blood relation and still go ahead with it.
I know some real cases of complex situations, so I can completely agree that being left at birth, or if a parent behave badly in various ways, that means a certain bond can be missing or be broken, and there can be a stronger bond built with someone else.
Actually, meeting again may even "backfire", the child may hold it against the parent who "deserted them" (in their view, at least).
Or the child may grow up with a sense of guilt like if it was their fault they were abandoned (that happens less rarely than it should, when one of the parents walks out when the kid is small enough, yet, old enough to remember the parent).
These are only to example of what can happen.
Though no worries, I did understand you have nothing against the incest patch, I am just adding my two cents to the conversation (and yes, I know we are talking about a game, sorry if it sounds too serious to some).