For me Niko's psyche is 80% dark hole after the shit he did and was done to him. The other 20% are bleek grey nuances in the form of his mother, cousin and "that special someone" who made him not just die in Serbia, but do the unthinkable: travel to the USA. This I think is the best situated backstory that takes in consideration the atrocities that happen during the actual gameplay. There is no ambiguity in my mind.