>>32957759Egg groups aren't based on biology, silly.
They're more like mating preference. That said, Gardevoir in the wild are most likely to connect with strong psychic/spiritual entities as a result of their empathic nature.
Doesn't mean it needs to be as such for it to work; hell, if a two foot tall cat and a forty foot long whale can make a baby two humanoids shouldn't be that far of a stretch