Do superheros,villains and love mix???

Does adding in a love life to a superhero make or break the character. To me all it does is add on another weakness that that superhero has.. Did writers just add them in to intensify plots. I think its a bad idea in general. Especially someone like batman who is to have very few emotions. this applies to villains also. Does Harley Quinn add to the jokers character?Or does she ruin his characters reputation of being heartless?