Scott Summers is Rachel's father...at least the one from her original timeline.  He is a mutant with the power to shoot force blasts out from his eyes as long as he gets exposed to the sun periodically.  They can be so powerful that he can punch holes through mountains.  He is codenamed Cyclops.  He can't control the beams from from shooting out  of his eys so he either has to keep his eyes closed or block them with a ruby quartz visor that can block the beams.   

Upon her initial arrival to the current timeline, Rachel kept the fact that she was his "daughter" a secret from him.  Most of the other X-Men of whom Scott was the leader knew well before he found out.  I suppose she feared that he would reject her so she kept it to herself.

Her "real" father had married Phoenix, not the original Jean Grey, the human, but the Phoenix Force that took over Jean's life.  So if you think about it, Rachel is the daughter of the Phoenix Force, not the true Jean Grey.  Confused yet?  Don't worry, so is everyone else.  LOL.

Eventually the Scott of the present timeline does find out about Ray being his "alternate-daughter" and he doesn't take it too well at first.  He eventually accepts it but doesn't form any kind of father-daughter bond with her.

Scott recently gave up his life to save his friends and the very future from Apocalypse, a very powerful mutant who believes strongly in survival of the fittest...as long as he is the fittest that is.

Whether or not Scott is still alive somehow has yet to be revealed.  There is soon to be a comic series where Jean and Nathan Summers go on a search for him.  If and when they find him, will he even be the same man?

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