What if Edgar the Atheling had gotten married and had children? (Let's give his decendants the surname Adelin) Who would he marry? Would he be given a Peerage? Will he and his heir's retain a claim to the throne? Discuss!!!
He had a good, hereditary claim to England. That, in itself, should be enough to get him a marriage to a rich heiress somewhere. His father had done that in eastern Europe; maybe Edgar could follow that example closer to England (i.e., in France or Scotland).
There were also opportunities in the Holy Land -- Edgar was friends with Robert Curthose, who could have helped set Edgar up with a barony.
Not really.
There are plenty of examples of the representatives of lost causes attaching themselves to sympathetic rulers either on principle or more often because the exile's claim could be useful one day. Malcolm III's reason for marrying Edgar's sister had to be because he saw some advantage in the Saxon claim. He could have tried to install Edgar as client king or, less drastically, used it for leverage in other ways.
[A few examples of exiles adopted as clients by outside rulers: Tostig; Edwin of Deira; William Clito; Edward the Confessor. Sometimes it worked out, sometimes it didn't].