What the Bible says about Sons of Belial
(From Forerunner Commentary)
He uses the words "father" and "children" in a well-accepted, spiritual way—that is, a son or a daughter can be considered the child of another if he or she shows the nature and works of that other person. Thus a "son of Belial" shows the characteristics of Belial, meaning confusion, though he is not physically Belial's child. A "son of Abraham," then, would behave or live as Abraham did.
John W. Ritenbaugh
The Holy Spirit and the Trinity (Part Three)