#mdl.

I think one of the things that bugs me the most about everyone immediately assuming that Abel isn't Adam's son just because he's blond, that I haven't seen anyone else really bring up yet is that. Blond hair gets darker as people age. It might be a recessive trait, but it's still possible for a blonde-haired parent and a brown-haired parent with the blonde allele to produce a blond-haired kid. (And tbh, to me Adam's hair looks more like an age-darkened dusky/dirty blond than a light brown, but that might just be me.)

We don't know how old Abel was when he was killed. Sources vary on that fact; I've seen sources that say they were adults who already had their own kids, that they were young adults, that they were teenagers, heck I remember reading a picture book in church when I was a kid where they were pictured as being twelve, maximum. Not all scriptures can even agree on whether Cain and Abel were twins or separate births, I've seen it written both ways! It's entirely possible that his hair simply hadn't darkened by the time he was killed.

I personally write Abel as being roughly 19 when he died (with Cain being closer to his mid-late 20's). My brother and I were practically platinum blond when we were little kids, his hair got darker earlier than mine did, but my hair didn't really start to darken until I was in college, in my early 20's. It's not outside the realm of possibility that Abel's hair just. Hadn't matured enough to darken yet.