The captivity of Elros and Elrond

[Artanis]

Then such few of that people as did not perish in the assault joined themselves to Gil-galad, and went with him to Balar; and they told that Elros and Elrond were taken captive, but Elwing with the Silmaril upon her breast had cast herself into the sea.

This quote is from the Silmarillion, after the 3rd kinslaying. It says that Maglor took pity upon Elrond and Elros, which probably means that if he had not intervened they would have been slain. Still, I do not see why Maedhros and Maglor took Elwing's sons as captives. What was the point? Why not simply leave them in the care of the remnants of the people of Eärendil and Elwing? Since Elwing was believed by all the Elves to have perished in the sea, and the Silmaril was believed to be lost with her, the boys were not useful as a way to put pressure on her. Besides, despite of the oath I have serious trouble believing that Maedhros and Maglor would sink so deep as to trade with the life of two children.

What do you mooters think about this?

Whatever the reason was, the children provided Maglor with an opportunity to get something significant in his life to care about other than the terrible oath. Perhaps that was his very motive for taking them. He was married, but his wife probably remained in Valinor and we don't know whether he had children of his own.