User blog comment:FairyRaven/Fairy Tail Chapter 427: Pitched Underground Battle, Review and Commentary/@comment-24784846-20150411000627

Well Mashima is clever. I THINK I discovered the origin's of Kain and Able's name origin, it comes from the Book of Genesis with Cain and Abel, the two sons of Adam and Eve. So them sharing a similar magic wasn't all coincidence, they could possible know each other, possibly be brothers.

Of course if Able did kill Kain that would be ironic because it states that Cain killed Abel out of envy.