Genesis doesn’t mention any love or affection between Cain and Abel. The Judeo-Christian version only describes Cain’s feelings of anger and fear. But other accounts tell this story in greater detail. According to University of Pittsburg’s D. L. Ashliman , these other traditions give us a fuller look at the relationship between humanity’s first brothers.
- The Koran describes Abel as subservient to his brother, beseeching Cain to do good, and promising not to defend himself if “Cain were to stretch forth (his) hand to kill.” 
- The Palestinian account shows Abel’s love and obedience even more keenly, commenting that “Abel was the stronger of the two, and would easily have prevailed against his brother. but he answered, If you stretch forth your hand against me, to slay me, I will not stretch forth my hand against you.” This version also introduces another plot element, the love triangle. Cain and Abel were both in love with the same woman. Here, this dispute preceeds their making of offerings to God. The offerings are merely the means of settling their argument.
- The Turkish account is similar, with Cain lamenting, “Oh father, let the girl born with me be mine!”  Here Cain is motivated by romantic jealousy. “Cain loved that girl exceedingly; so he went and slew Abel,” the text reads, “thus because of a woman was blood first shed upon the ground.”
- Another Turkish version shows how Eve intentionally induced the rivalry by holding the young brothers at arms length and commanding them to fight. Here Cain bit and drew blood while “Abel merely imprinted a long lingering kiss on his mother’s arm.” Eve declared Cain’s wickedness and set in motion events that would lead to Abel’s murder. 
- Lastly, Ashliman described an Italian folk version that begins with: “They were two brothers. Abel greatly loved Cain, but Cain did not love so much the brother Abel.” The folktale goes on to tell us that “Cain also was a good man” but that his failures drove him to jealousy. And, most surprisingly, that “Cain greatly loved God; he was good towards God, more so than Abel, because Abel, having become rich, never spoke more unto the Lord.”
 Dr. Ashliman’s CV can be found here.
 These are my summaries of texts compiled, revised and/or translated by D.L. Ashilman.
 As follows the logic of creation myths, the woman in question is Cain’s unnamed twin sister.
 I find this compelling as a natural counterbalance to the Genesis account. Here it is a mother figure that ignites their rivalry.