reading spoilers from below doesnt help me understand the incest tag lol

Well, they are all Gods. Maybe they want their offsprings to be A full God also? And not some demi-God ? Hehehe

it's incest cause they are brothers and sisters. Also in ancien egypt royal offsprings were born from incest between brother and sister)

technically since they are gods, they have no dna so it's incest, but not really incest