Cain and Abel were figures from the Bible.
In the story, Cain killed Abel with a rock. (PROSE: Christmas on a Rational Planet [+]Loading...["Christmas on a Rational Planet (novel)"])
Cain and Abel of the Imperial Marines chose their ordained names together. Cain wondered how the biblical Cain would have turned out if he was given a second chance. (PROSE: One Bad Apple [+]Loading...["One Bad Apple (short story)"])