"The Marvel Universe, by contrast, has always glorified in the proliferation of timelines to an extent that it sometimes becomes almost impossible to keep straight in one's mind, yet somehow it remains accessible to most examples: Rachel Grey is the daughter of Scott Summers and Jean Grey but was born into a timeline, came to the present from a dystopian future that never happened. Cable, her half-brother, Summers' son by Madeleine, the woman he married when Jean was supposedly dead, was sent into the future to have a disease cured and came back when he was significantly older than his father."--Roz Kaveney, Superheroes! Capes and Crusaders in Comics and Films.
I'm still waiting for the story where it turns out that Cable is his own grandpa. Granted, it would mean displacing Corsair, but I think we'd all be okay with that. Anyway, Kaveney's book is very good; it balances accessibility with depth to make a real study of what makes superhero comics worth investigating.