Responses
I think the author wanted to make him obsessive with Anton, since he is the only thing left of the woman he loved. Why exactly he choose this approach and had this kind of possessive-obsession (even sexual desire) is not clear at all. The father’s character is one of the weakest points in this story, since, as you said, it‘s not clear why he‘s doing what he‘s doing.
I'm still confuse, why his father did that? make anton misserable, punish him with he can't own arwin. Is it revenge cause he lost his wife? and his family doesnt like her?
and is anton cousin's child? still mystery but I want it to know the truth