Jormungand

Jormungand, also known as the Midgard Serpent, is the son of Loki and Angrboda. Jormungand is a beautiful naga who is falsely portrayed as evil in the written mythologies. Jorm is actually a very sweet guy, and yes he does have a grudge against Thor. That's because Thor lobbed Mjolnir at him one day while fishing with the giant Hymir. I'd be pissed too.
Jormungand's sisters are the lycan Fenrir, and the queen of the underworld, Hel. They were stolen from their mother at a very young age because the norn Skuld falsely fortold the destruction of the world at their hands. Hel was sent to the underworld where she'd rule. Fenrir was kept in Asgard at Odin's request, and Jormungand was cast into the ocean where he would stay until Ragnarok. He's supposed to kill and be killed by Thor in the final battle of the norse pantheon, but I'll be damned if Loki's family comes to any more harm than they've already suffered.