Golbez being the 13th's counterpart or precursor to Eden, essentially? Possible. Really not sure about the fatherhood, but possible, also, I guess.
I think there's a fair chance Golbez is gonna turn out to be the Azem shard of the 13th and that's what's unique about him. He does seem to be the Darkness version of a Lightwarden, giving out power and drawing in forces. But drawing in companions is also an Azem quality. "Shepherd to the Stars in the Dark" and all that.
I really hope this patch gives us a more definitive answer as to what his goals are. I have a theory that he's trying to make it possible for the denizens of the 13th to die by connecting the 13th to the Source, which has a properly functioning lifestream. The 13th's seems, to me, to have merged with the physical shard itself and that's why they can't stay dead. They essentially don't go anywhere when they get killed, so they just coalesce in place after enough time. If Golbez is related to the start of the voidsent somehow, or at least to the ruining of the 13th shard, then him wanting to fix things somehow would make sense.
I just really don't think he's just trying to invade/conquer things for power's sake. I can't see someone like Rubicante following him if that was all he was. And he says Golbez spoke to him of salvation.