The question of 'what is a GF' has always kinda troubled and confused me. I still have the facts about their nature and source down in my head to this day, and it annoys me that they seem so inconsistent:

- GFs can be drawn from living things. The living things GFs are initially drawn from don't seem capable of summoning them.
- GFs appear to feed on the memories of their users, or at least cause memory loss if junctioned for a long time.
- They're somewhat mortal, so they can die. But they don't seem to age, either. See Bahamut, who had been sitting around collecting dust for centuries... same for the brothers Sacred and Minotaur.
- Like Sacred and Minotaur, they don't seem to die with their users. They don't need a human mind in order to exist, so they're not brain monsters.
- Are the non-junctionable GFs actually GFs?? I mean, this actually includes Moombas, MiniMog, Chocobos and GILGAMESH.
- You draw Cactuar from Jumbo Cactuar and Tonberry from Tonberry King. Siren, sorta wind elemental seeming, is drawn from Elvoret, a wind elemental, and Griever is (presumably) drawn from Squall. This would make one assume that they're extensions of the self, but AGAIN, they can be drawn from multiple sources (Eden can either be drawn from Tiamat or Ultima Weapon) and sometimes their sources aren't even living things (Doomtrain has to be assembled with items).
- They can be junctioned, transferred digitally, and stored in a database like data, but they definitely have a physical form as well.
Using this knowledge I can at least assume that GFs aren't really Gods, but they are godlike in that they seem to link themselves to certain beings and kind of define their traits, like a zodiac. So to the real point; is Griever an extension of Squall's mind/soul? Did he make Griever up with his wishes and deepest darkest secrets? Uh... probably not. But he might be Squall's 'zodiac creature', at least.

Jodo's probably got a good idea there, though. It's not like we know HOW GFs are made. For all we know, they are like Aeons, and Griever is like Squall's berserkified future self after he's died.