"Genetic" can also get more complicated than just one or both of one's parents' obvious traits, going back to grandparent(s), great-grandparent(s), or signs manifested in uncles, aunts, cousins -- i.e., picked-up from one or more distant common ancestors. Sometimes you can even get two recessive genes together, in neither of which person were there any signs, and combined they produce something 'full-blown.'
This applies to any kind of genetic trait, not necessarily Autism/A.S. My brother and I have blond hair, but I can't name a blond ancestor, though we have blond(e) aunts and cousins. May be a "throwback" trait that's been hiding in our family's gene pool for numerous generations until just the right combinations or mutations brought it back out in the open. (I suspect he'd also be as Aspie as I am, though not in the same ways!)
My mother I'm pretty sure is Aspie, but it's not "over-the-top," just like mine isn't, though mine is more strongly Aspie. Dad has an MR sister; connected? Science doesn't know for sure. Mom says her whole family are/were "frustrated intellectuals;" we're from Lower-Working-Class, so my generation was the first to complete college, and me only thanks to Student Loans.