Genes are no longer genetic?

Pretty sure Moira McTaggarts parents are non mutant.

You can have dormant genes. For example cyclops comes from two nonmutant parents, and those two nonmutants passed on dormant xgenes to 4 mutant children

Yeah it happens either way.

The same way you can have a blond mother but not turn out blond yourself. You might carry the gene for blond hair but it might not be active

Exactly^

But for her to be blond someone up the line had to be blonde. Genes don’t just appear. For him to be a mutant someone in his family has to be mutant

Yes but again, nonmutants can carry a recessive dormant xgene which can be passed down to their children, which then can become active.

So for example, i can have two parents who arent blond but carry a recessive gene for being blond, and i could end up blond as a result.

So two parents can have recessive dormant xgenes, like cyclops's family, but when they're passed down to their children they may become active. Which is why a family like the summers has two nonmutants producing four mutant children

So sue and reed might not be mutants but they could carry the xgene and pass it on to franklin.

As we see above that isnt the case in this situation, but its not unlikelym its actually pretty common. Many mutants come from nonmutants.

Its also possible for two mutant parents to produce a nonmutant child

The Mayday Parker effect. Peter had powers when she was conceived, she was born with powers, and a sentinel even identified her as "beyond the range of embryonic normalcy", but she's not a mutant.