Since there is no test or requirement of sexual activity in a marriage, there is no reason why fathers and sons, or mothers and grand-daughters, or even fathers and daughters should be prohibited from marrying each other, given the new elastic understanding of marriage.
IIRC a Roman Caesar married his horse. Isn’t that where the degenerate clique wants to take America? Of course it is, so the degenerates will have no restraints upon them and they can magically think they are normal.