Nephilim?.......................
Humans.
If they breed together, they ate the same species together.
Nephilim?.......................Cain and Abel.
Nephilim were ‘giants’. Neanderthals were shorter but heavier than the typical Sapiens.
There is a midrash that says the world was created and destroyed 974 times before the first Adam. Those worlds varied in their resemblance to the Creation as now known, thus ‘explaining’ Nephilim, Repaim, Neanderthals, Denisovans, and perhaps other remnants similar to Sapiens.