A bastard/illegitimate child conceived while one or both of the biological parents was fighting with their significant other and were on a "break" from their relationship.
Mary and I were fighting and she kicked me out, so I went to the bar and banged this chick in the bathroom and now she's about to have a god damned breakbaby!
There's a social situation and everyone wants to do something, but nobody wants to be the first person. The first person that does so is breaking hearts.
Derived from the card game Hearts.
Everyone wanted some candy from the communal bowl, but we were all waiting until someone else would break hearts.