This article contains spoilers for X-Men Legends #2
Marvel has finally explained the greatest mystery of Cyclops' origin. When Stan Lee came up with the idea of the X-Men, it was essentially something of a "Get Out Of Jail Free" card. He was getting tired of having to create origin stories for all his superheroes, and the idea some people just happened to be born with superhuman powers made his job a whole lot easier.
It didn't take long for later writers to create origin stories for the original X-Men. Take the example of Scott Summers, a.k.a. Cyclops. His backstory is absolutely fascinating; Scott and his brother Alex were orphaned at a young age when the plane their father was piloting was intercepted by an alien spacecraft. Scott and Alex parachuted to safety, but their parents were taken by the Shi'ar. It's a story familiar to most long-term X-Men readers, so much so that one unanswered question has gone almost unnoticed. Why was the Shi'ar visiting Earth in the first place, and why did they kidnap Cyclops' parents?
Fabian Nicieza and Brett Booth's X-Men Legends #1 finally provides an answer to this unasked question. The story is set years ago, with Cyclops and Havok learning they have another forgotten "brother" – Adam-X, who sometimes goes by the codename X-Treme. According to their father Corsair, former Shi'ar Emperor D'Ken was conducting a eugenics program in which he merged Shi'ar DNA with that of other races, hoping to advance the deteriorating evolution of the Shi'ar race. This explains why the Shi'ar visited Earth in the first place, and presumably indicates they also kidnapped subjects from countless other worlds.
Adam-X was, therefore, one of D'Ken's creations. He is technically part of the already-complicated Summers family tree in a way only possible in the crazy world of comic books; what's more, amusingly dialogue in the comic suggests D'Ken could well have created other human-Shi'ar hybrids, meaning there may be other Summers siblings in Shi'ar space. It would make sense for the alien emperor can be intrigued at the possibilities offered by merging human and Shi'ar DNA, especially given the propensity for genetic mutation in the Summers' family line.
The classic X-Men villain Mr. Sinister conditionally maintained that the Summers line was the key to the future evolution of the human race, and it is possible D'Ken's agent goes to kidnap Cyclops' parents because their advanced technology suggested the same. This plotline has been neglected in recent years, but it is important to note Jonathan Hickman's X-Men relaunch has placed the Summers family at the center of the new mutant community on Krakoa, so it is possible it will be revisited soon.