I've been writing my postie, sorry it's taking a while, I have an upcoming Calculus final.
In the meantime, though, I've come to realize something. Alex is totally taking Jason's death like a child, not one who's so young that he's incapable of comprehending death, but not one that's old enough to come to terms with it either. He just can't... deal with it. Jason's death was so fundamentally profound and life-shattering that it broke something in Alex, and that's not healed, not by a long shot. It hasn't even begun to. I don't think it ever will.
I could totally attribute that to Alex and Jason being Alpha and Omega since those two were-creature/were-creature mate roles are so intimately and profoundly bound that losing one is almost irrevocably harmful to the other. Despite that, though, I think that the reason Alex was so attached to Jason, to such a degree as he can't let go is because he is, for one thing, gay. It's never mentioned in publicized canon lore, but Alex has had quite a few failed relationships. Jason kind of had one, but was outed because of it. I think that there was a point in his life that Alex had given up on ever finding a mate and Jason just managed to just waltz in and steal his heart away... In a sense, Jason saved Alex from the very same fate that his older brother Nathan suffered.
There's that fact that human!Alex is very much an affectionate character, needing affection as much as he likes to give it to Jason, but there's also the fact that Jason fulfilled the needs of were-lion!Alex in such a way that no one else was able to back when they first met. I'm of the opinion that it's not only the Alex's and Jason's biologies that are contributing to such a profound and strong bond that Alex just can't let go, but it's also their psychology that's to blame...
I have no idea why I was pretty much going on a character exploration tangent... >_>