So, in the family tree Kalle and Velna are listed as offspring of the starting hero; when Kaisa gets added, she's listed as offspring of whoever introduced her. In all these cases there's no suggestion in the text that there's an actual blood-relationship.
There are two possibilities here. One, the tree can't cope with unattached branches yet, and this is intended for a future release; or two, the tree represents some sort of patronage system, possibly interlinked with symbolic adoption (like the Romans, or maybe some kind of moiety system). If so, this needs to be a bit more explicit, because otherwise players will assume it's meant as a literal family tree (and thus a broken one.)
More long-term, it would be awesome if cultural decisions affected which family relationships were possible and how those relationships functioned. (Yeah, I know how easy it is to think of six awesome bloats before breakfast. Apologies.)