You can't even date Doug in RF4 without completing the main storyline first (he stays at 3 hearts until you do) and all of the events including love events in that game are random, and Ford's heart events seem to be pretty specific about time and place in order to activate them (one event requirement is to speak to everyone in Westown, Dessie, Inari, & Witchie). I've got my work cut out for me...