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 power leveling 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.