Four years after Cable’s first appearance, his backstory was finally revealed in the four-issue miniseries The Adventures of Cyclops and Phoenix — the two lead characters of which are Cable’s parents. Sort of.
As it turns out, Cable’s full name is Nathan Christopher Summers, a.k.a. the son of Scott Summers — Cyclops, a founding member of the X-Men. While Scott’s paramour has long been Jean Grey, Nathan is actually the child of Cyclops and Madelyne Pryor, a perfect clone of Jean Grey who emerged while Jean was presumed dead. When the real Jean returned and the fake Jean was dealt with, Scott and Jean took Nathan into their care, finally united as a family — for about five minutes.
For reasons unknown at the time, the infant Nathan was infected by the mutant Apocalypse with a variant of the techno-organic virus, which rapidly turned one of his arms bio-mechanical. The parents, their child in peril, were then suddenly visited by a mysterious woman who introduced herself as a member of the Clan Askani.
The visitor told the duo she could save their son — but only if she took him from them, to cure him in the future of the alternate world of Earth-4935. Seeing no other choice, the parents handed over their child, expecting never to see him again, but hoping he would survive.
He would survive, of course — and though they didn’t know it when they handed him over, they were going to be there with him to help.