I saw this and thought I'd share with you all.
Sons of Fenrir: Hati and Skoll
"When the Great Wolf, Fenrir, began to run amuck, he first went back to the place where he was born. Tyr and the other Aesir had tried to keep him from going back to the Iron Wood, but one day he escaped and fled to his birthplace, and was reunited with his mother Angrboda, and his werewolf half-siblings. It is not known what happened to him there, save that when he left, his maddened devouring rage had begun in earnest, and a wolf-woman of the Jarnvidur had borne two wolf-pups, the very image of their father. In another account, the mother of Hati and Skoll was Angrboda herself, by Fenrir her son, but we may never know the truth of this. Skoll's name means "treachery" in Old Norse, while Hati's name means "Hater". Hati is also sometimes given two different last names - Hróðvitnisson (Son of Rage) and Managarm (Moon-hound).
When Fenrir was chained, Hati and Skoll were the only ones who came to defend him. Loki and Angrboda themselves did not interfere, for they understood the nececessity of the binding, but his young sons tumbled forth in a vain attempt to free their father. Instead, they were captured by the Aesir, and Odin put them to use, bespelling them as he had bespelled the Great Snake. Sunna and Mani had often been known to dawdle or change their course, which meant that the days and nights were not always dependable and on time. Mani was especially bad at this, as he liked to look down on what was happening, and the adventures played out below his feet enchanted and delayed him. There had been complaints about this from many mouths, and so Odin put the two wolves into the sky as a way to make the chariots run on time, as it were. Skoll was bespelled to chase Sunna's chariot as a dog herds sheep, keeping it to its path, and Hati (also known as Hati Hridvitisson, and Managarm) was similarly charged with herding Mani's dog-cart.
While they do not spend all of their time in the sky - when the Sun and Moon are on time and stick to their schedules, the wolves can run free on the earth below - if either sky-etin is late, they are lifted into the sky to do their job. Skoll is the quieter of the two, and says little; he does not love the involuntary nature of his job, although he gets some fun out of racing Sunna, but he is aware that it is a better deal than the one that befell his father. Hati is more outgoing and more moody; he veers from cheery mischief to wrath, and deeply resents the spell that pulls him so often to the sky. Both are aware that if Ragnarok comes, they will be able to chase and kill Sunna and Mani, and free themselves from Odin's spell, and they look forward to that day."