Well, for one, most of the Viltrumites look no different than the Earthlings, so write that down… /hj

I would just chalk it up to “the aliens aren’t all that different from humans, so ‘mixing’ wouldn’t necessarily mean the children are gonna be more like the aliens than the humans.” Also conversation can get very weird if someone was to veer it a certain direction.

This question now makes me think I should go through the first season again. I forgot about that moment entirely.