House Sparrow Passer domesticus
I am not quite sure how this came about but in our yard we have one male House Sparrow feeding a single offspring. The two birds are basically inseparable and the young one wastes no time soliciting food by wing fluttering and cheeping on a constant basis. I have no idea what has happened to the female, or presumably to other members of the same clutch, but one certainly could not fault the dedication of this male in feeding his progeny.
When one takes into account the fact that DNA studies often reveal mixed parentage in the same clutch of eggs, one can only hope that the effort this adult is making is invested in his own genes!