Ok, here's the deal.
Started playing in Sunlight Tides. My sim waited for the love of his life (Maggie Strong) to became a Young Adult, and then he moved in for the kiss and wedding and woohooing for nooboos. I didn't want her father to be left alone, so I brought him along as well. When he arrived, I discovered he was a witch (game turned him one at start), while his daughter, Maggie is a normal sim.
Does witchiness have any chance at all of being passed on to the grandchild in this case? Or is it a case of neither parent is a witch and so the grandchild will likewise also not be a witch?