Humans possess an evolved mechanism for incest avoidance that is triggered during childhood by cues like seeing a mother care for siblings or by long-term co-residence.

“So one unmistakable cue that someone is a close genetic is a sibling is you see your mom and to the extent you've met the right woman as mom uh your mom you know pregnant give birth to caring for breastfeeding a newborn that is an unmistakable cue that that their kid you know breastfeeding from my m”