You could have it as a flashback when the child was quite a bit younger (10 or so) with the father and they were going on a hike (or some activity) and he/she as the child finds the father an amazing role model and person and really looks up to the father. As he/she gets older this can change. Evtually as you said the father will pass and the older character now will have changed because of this.
so on the positive side it could help them conmunicate but on the bad side what if your dating someone online you dont who they are good way to get kidnapped