So….I don’t know if anyone else has talked about this, but I think that Keith’s father left him. And though it is long, here is why:
When Keith hears his father’s voice, he’s shocked, but not completely horrified. The first words he says aren’t “I thought you were dead!” or anything similar, but instead
He even has the chance to ask how he might be alive (or like…anything similar) or what he’s doing there, but instead he goes right to, “What’s going on outside?” because that matters more to Keith than what his dad is doing back in their shack. And then his dad says:
“Don’t you want to catch up?” is not something you tell somebody when you’ve died, but when you’ve gone away for a while.
Keith’s response is “Of course I do,” but look at his expression. He doesn’t get it- and of course he wants to know what his dad has been doing, but he’s still confused and cautious.
Now, we already know that what these holograms do is pair Keith’s greatest hopes with his greatest fears.
We’ve also seen it before- it showed him Shiro, but hologram Shiro told Keith that he should give up the knife, and that choosing to find out his own past was selfish. That doesn’t stop Keith, though: “I’ve made my choice.” He doesn’t care if Shiro thinks he’s being selfish. What Shiro says and does next, though, is what makes him stop:
And then Shiro starts to walk away. Only then does Keith actually stop. Only then does Keith decide that maybe it isn’t worth it. Keith actually calls out to Shiro, and then starts to run after him.
You can tell from his expression, and from the fact that he literally runs after Shiro to stop him that Keith is desperate. Why?
Because one of Keith’s greatest fears is being left by the ones closest to him.
Why would this be one of his greatest fears?
Because it has happened before.
He follows Shiro and finds himself standing in front of the door that another person he cared for walked out of.
And once again, one of his greatest hopes is paired with one of his greatest fears. He wants to know about his past- that’s one of his hopes, but why would his father be the one to show him that, unless
One of his greatest hopes is that his father will come back.
This also makes the line, “Don’t you want to catch up?” and the fact that Keith doesn’t even ask why his father is back even more important. This is a scenario plucked from Keith’s mind: it’s a fantasy. He doesn’t necessarily want to know why his father might be back- there doesn’t have to be a reason. He just wants him back, anyway.
His other greatest fear, though, is that the Galra will come to Earth, and destroy it. In the end, the Earth matters more to Keith than his own father and past do, and maybe part of that is because he knows that his father didn’t care enough about him to stay.
Keith still hesitates, though.
Walking out that door means turning his back on his father, and what he thinks might be the last chance he has to know anything about his past. But he walks out anyway.
He looks his father in the eye as he says this. He doesn’t apologize, he doesn’t justify himself, he just says goodbye and leaves. That doesn’t strike me as the farewell somebody who was close with his father would give them as they walk out. And look at his expression? He’s not sorry. Maybe he’s hurt and torn, but more importantly, resolved. He is leaving, and his father will not stop him.
And also- neither of them acted like they were particularly close, either. There were no reunion hugs, and the only one who even smiled was Keith’s father (albeit somewhat creepily, but that’s irrelevant). And Keith wants to see his father again, but that doesn’t mean he would be happy if it happened. They didn’t part on good terms, however it may have happened.
TLDR: Keith’s father didn’t die, but left Keith many years ago- and because of that, one of his greatest fears is that Shiro, the only other person he’s become very close to, will do the same.