If you're wondering who the Hodir that the Sons are sons of is, well, some clues are revealed in the quest Fate of the Titans, given by the wandering Titanic construct Creteus. Hodir is apparently one of a class of Titans or Titan creations (it's hard to tell which) called Watchers, and was entrusted with guardianship over the Temple of Winter after the Titans stuck the Old Gods into their prison within Azeroth. If you've run Halls of Stone and witnesses the Tribunal of Ages event, it's implied that the various entities like Loken, Thorim, Freya and Hodir himself were either appointed to watch over "Aesir and Vanir or in common nomenclator Storm and Earth Giants" or they were Aesir and Vanir themselves, meaning that Hodir is either a very old and powerful giant himself or a form of Titan or Titan construct. Not only are we unaware of exactly what Hodir is, we're not even sure exactly where he is, or most of the other designates either. All four of the watchers mention in Fate of the Titans, including Hodir (the designates mentioned in the quest are Tyr, Mimir, Freya and Hodir) are missing from their appointed temples. Investigating the Temple of Winter reveals that sulfurous entities of some sort killed the guardians there.
While we know that the Dragon Aspects were appointed at the same time to monitor the evolution of life on Azeroth, Hodir and the other designates seem to have been more focused on preventing the Old Gods from interfering with Azeroth and the compound at Ulduar. The Tribunal of Ages states that there was a global war between the watchers which began and ended with Loken who "neutralized all remaining Aesir and Vanir affecting termination of conflict " and then put the Vrykul, Earthen and other Titan constructs such as giants into some form of stasis. So it's possible Hodir is dead, or possibly just stuck inside Ulduar in the same manner as Thorim.
While we don't know what happened to Hodir, what happened to his people is fairly clear: Loken didn't want to fight Thorim in a straight up fight (since he'd lose) so he pinned the murder of Thorim's wife Sif on the Frost Giants (most likely their now deceased king Arngrim, who enjoyed a good meal of gigantic wyrms in life, and even in death still enjoys a squrimy repast once a day) leading Thorim, who is a very action oriented guy, to go declare war on the Sons. (It's not clear where Hodir was at this time. Was he already gone? Did Loken arrange for this little distraction to keep the other watchers off guard while he took them out one by one? We don't know yet.) After creating the Thunderfall region, Thorim slunk off to brood atop his Temple of Storms for a very long time, because the king of the Sons of Hodir (again, most likely Arngrim) placed a rune on the hammer preventing Thorim from getting it back. King Jokkum, the current ruler of the Sons, says it was the last thing his father ever did. Since you can find and accept quests from Arngrim's frozen corpse (which looks much like the frozen giants and dwarves in the Thunderfall, except it's seated) this would seem to confirm that Arngrim was indeed the patsy for Loken.
At some point either during or after this particular bit of bad business, the Sons found themselves at war with crazy Vrykul women who want to replace Sif as Thorim's wife. It's unclear why this war started, although it may have something to do with the Frost Vrykul just being loyal enough to Thorim to keep fighting after he stopped. When you arrive in the Storm Peaks, you soon find yourself embroiled in this ancient conflict, first on the Vrykul side, then after speaking to Thorim you end up helping the Sons in order to get Thorim his hammer and armor back. This leads Thorim to go fight Loken and you should really do that quest chain if you haven't already, I've probably spoiled it more than I should as it is. You're then tasked by King Jokkum with getting even, because by this point the giants are fully aware that Loken set them up in the first place, and also to kill Volkhan while you're at it. In order to get this far you will have had to do a series of quests retrieving various artifacts for the Sons, including the anvil of Fjorn, a fire giant. Thorim is actually the guy who asks you to whack Fjorn as a make up gift to the Sons, which begs all sorts of questions. Why do the Sons hate Fjorn and Volkhan? Are the fire giants responsible for the sulfur left behind at the Temple of Winter?
At any rate, the Sons will eventually task you to retrieve various artifacts of Hodir, including his spear, horn and hat (you can see my warrior floating in front of Hodir's chapeau in the accompanying image) which you then have to spend a lot of time thrusting, blowing and polishing in order to get the Sons to really like you. It's all ludicrously boisterous and almost parodically hyper-masculine, broken up only by feeding worms to King Jokkum's deceased father Arngrim and doing favors for a giant worg. The entire time I was working on these quests, I half expected King Jokkum to ask me if I liked gladiator movies.
And this is pretty much all we know about the lore behind the Sons at this time, although I'm sure Ulduar is going to reveal the ultimate fate of Hodir and the other watchers when the raid is finally introduced. I hope they're not dead or worse, forced into slavery to Yogg-Saron, but it's not looking good for them. Hopefully the Sons will get a chance to mount some sort of rescue operation. They have all his stuff in pristine condition by now, considering how much work legions of adventurers have put into maintaining it.