I get a little giddy whenever family trees in 'Harry Potter' start getting messy, because the idea of a squib living inside a magical dynasty is such a small, human crack in an otherwise fantastical world. From my perspective, squibs absolutely can inherit the genetic potential for magic even if they themselves can't perform it. The books and extra material hint pretty clearly that magic runs in families but doesn't behave like a simple on/off switch. There are households where every child is magically gifted, and then a surprising squib appears — that suggests polygenic
inheritance, variable expressivity, and things like incomplete penetrance. In plain terms: the genes or magical tendencies can be present but not expressed.
Thinking of it like a real-world trait helps me make sense of it. Imagine a family where some members have brilliant musical talent and others don’t, even though they share genes and the same home. Maybe the environment nudged some kids toward music, maybe the particular mix of alleles mattered, and sometimes a rare combination just didn’t trigger the trait. Replace music with magic and you’re in squib territory. J.K. Rowling's wider notes also imply that squibs come from wizarding families on occasion, and Muggle-born
witches and wizards show the flip side — magic can pop up unexpectedly, suggesting a complex inheritance model rather than a single magical gene.
Beyond genetics, I like to entertain other in-universe explanations: magical potential could require certain developmental conditions, exposure to specific artifacts, or even emotional thresholds to 'awaken'. That fits with characters who show delayed manifestations or unusual forms of magic. For a squib’s descendants, the odds aren’t zero; a squib can have magically talented children if the right mix of magical alleles meets another magical partner or some activating factor. Practically, that explains why some family lines swing between Muggle-borns, full-bloods, and squibs over
generations. Personally, I find that unpredictability heartbreaking and beautiful at the same time — it makes every character’s magical identity feel earned and fragile rather than guaranteed.