A lot of people didn't like the beginning too much before the tragedy happened. I'm not sure if for them the game had improved if I had build more of a father-son relationship here.

I have seen games handle this in s couple of ways I can think of off the top of my head.

You could start play as the father for the first coupla easy missons

Alternatively you could have the father with the son for a number of early 'missions' as a sort of walk-through/easy/training mode. (comes along with a torch/lantern for parts of the early missions, or something)This effectively builds a low level of dependency. (Gotta go back and check something at camp *ACK* I am dead.)

You could also have the player complete tasks for the father (let's say retrieving the runes and bringing them back), and then put them in a position that forces them to fail. As you bring the runes back he can provide back-story. Once that is sufficiently developed then you put them in a situation that is timed, or that required a number of runes, or both (oh noes, I am poisoned and require a certain number of runes to cure myself.) The son could get back in time to hear/see the father die, but too late to save him.

Anyway, like I said: these are just off the top of my head. I am sure that other people can think of more and better examples.

Also: have him turn into a red-eye-monster as a possibility.

Also: some Lovecraft might help here: this: http://www.hplovecraft.com/writings/texts/fiction/cs.asp, or this: http://www.hplovecraft.com/writings/texts/fiction/mb.asp, but really any of his writings might give you ideas for how to convey the flavor (out of space) of your story.