Those are indeed rather low heart rates. I've seen lower ones discussed on this forum, but even so, anytime--anytime--fainting occurs when you've got a low heart rate, it's time to bring it up with a doctor.
It looks as though your fiancé does indeed have a family history of this kind of thing, but that's not necessarily OK, because, for example, fainting can cause serious head injuries. Also, picture driving along at highway speeds and having a sudden faint? It could be a Bad Thing for many people.
Take this to a doctor and get an evaluation and some advice, for the sake of everyone's safety.