Grandpa was a redhead — light red/blonde.
None of his eight kids had red hair.
Several of his grandkids have red hair in different shades.
My great grandmother was a redhead. Right off the boat from Ireland. I got those genetics. I was a carrot top as a kid and eventually went blonde then bald.
One feature of red heads is reactions to medications. Red heads react very differently to meds than most everyone else. I get the side effects but not the cure.
When I went on blood pressure meds, I had to play a roulette of finding a medication that actually worked.