Harry Potter Headcannons

Chapter 123

What if the gift for magic existed on a recessive allele and in order to have magic you had to have two recessive alleles. If that's true it would make sense for two muggles to have a child with magic, the two muggles could each have for example Mm and Mm which would give them the possibility of having a child with mm which would be the gift of magic. This would also make sense with why two muggle-born witches and wizards seem to be able to always have a magical child or why a muggle-born parent and a half-blood or pure-blood parent are also able to have all magical children.

As far as squibs go there could also be other factors that would block it even if the child should have magic, or another possibility is that a traumatic event that the child experienced before they were old enough to show signs of magic blocked their ability to use it.