Anyway if you're not convinced this is the best possible choice, later X-Men writers tried to set up Gambit and then Apocalypse as the long lost Summers brother.
Cyclops' brother Havok has had a long lasting relationship with Polaris that almost lead to marriage a couple times.
Polaris is sometimes the daughter of Magneto and the sister of Quicksilver and Scarlet Witch, currently Magneto's only child.
Scarlet Witch was once married to Vision, and that relationship has a chance to come back soon.
Vision was constructed by Ultron, who now that I think about it had his brain patterns based off of Hank Pym while Vision's were based on Wonder Man's, so there's some more to this family tree.