That's my point, it's not usual for them to be this random. You didn't have three otherwise genetically similar mammals in the Cretaceous Period trying out six eyes, three legs and two tails all at the same time, for example. Mutations are usually much more subtle than that, and even if there is a major development, it's unusual for creatures that aren't otherwise closely related to share similar traits. My parents weren't mutants, and neither were Erik's or my sister's, yet we still share the same gene, it just expresses itself in a different way. It would make more sense if, say, I'm a telepath, and then my children were also telepaths and so on and so forth.

But even that doesn't seem to be true for us, as in another universe, Erik's children's mutations aren't similar to his at all. There's a theory that the advent of the nuclear age sped along the process, and might have something to do with the extreme variation, but there's been no way to prove it yet.