[Tempester]

Originally Posted by Kanon

The resemblance might actually an actual plot point. I'm starting to think Shou is the father of both girls and that the heteropaternal superfecundation is lie the family came up with so that they could have at least one "proper" heiress.

Here is a detail from the VN, which probably won't be covered because the anime skipped this whole part and is already going into later scenes. I hope I can clear up some of the confusion in this thread regarding why they didn't try a DNA test.

Spoiler:

After Shou was imprisoned, the family wanted to prove which girl was his child, so they actually did decide on a DNA test. The thing is, Shou absolutely refused to take part in the test, despite how the family offered to bail him out of prison if he consented. With no choice, the family decided that the "better" of the twins would be the heir to the Futakis.