As we know, Marty McFly (BTTF) is the 3rd child in the McFly family in 1985. In BTTF (1) we see in the picture of all three children that they progressively fade out. I understand why this is the case, but why would Marty be the last one to fade out and not the first, as he was the last one born?
It seems that the changes in the timeline cascade forward, affecting temporally displaced facts in order of how far removed they are from the moment of distortion. Marty faded last because his birthday is the furthest away.
Were it not for his siblings fading in the same order relative to each other, it might also be possible that Marty's displacement itself offered him some kind of protection.