OK dose this mean that if you were to go back in time and kill your grandfather, that you wouldn't exsist? Or am I totally wrong? Explain/Discuss. :)

EDIT

Your grandfather before your father exsisted?

I would guess that killing your grandfather would cause a split in time and you would continue to exist, because you are still born in the other, (original) string in time. Though you wouldn't exist in the other string because a whole new reality would be created.

though i do think the concept of time travel to the past is a little bs, i would agree with alternate timelines

No time would be split... It's called a paradox for a reason. You just couldn't do it because you wouldn't exist if you killed him but if you had gone back in time and killed him, then that was already something that happened in his lifetime and there would be no way you'd ever be born anyway. None of it is possible that's why scientists love to talk about it.

The multiverse model is the only method that I know of for reconciling that paradox.