Third Summers Brother

The third Summers brother is a plot point in X-Men comic books regarding the family of the superhero Cyclops, alias Scott Summers. The plot point was first referenced by writer Fabian Nicieza in X-Men vol. 2 #23 (1993), published by Marvel Comics. In that issue the villain Mister Sinister has a conversation with X-Men member Cyclops and casually mentions Cyclops' "brothers." Cyclops notes that it is odd to talk about his brothers in the plural, since as far as he knows he has just one brother (Alex Summers, also known as Havok). However, the dialogue does not mention three, implying there could be several brothers still in existence.

While Sinister himself immediately claimed that it was just a common mistake of his the speculation about the mysterious third Summers brother ran rampant among fandom for many years. The question "Is there a third Summers brother?" lingers during years and is one of the most important questions of the main Marvel continuity which included "Who is Nightcrawler's mother?" and "What is Wolverine's origin?".

Gambit (due to his energy abilities) and Adam X (who may in fact still be a brother to Cyclops and Havok) were both believed to be one of the missing brothers at some point. Marvel revealed a third Summers brother, known as Vulcan, in the 2006 miniseries X-Men: Deadly Genesis.