system
Given the following post, respond as if you're commenting on Reddit:
human
[Harry Potter] Did this whole avada kedavra bouncing back at the caster because of love thing ever happen in the history of the world other than with Harry Potter?
gpt
The key thing here isn't just love, it's that the protector had to be *given the option* to leave and save themselves, but to refuse it.  After all, James Potter died protecting his son as well, but he didn't give Harry any protection, because Voldemort killed him fighting and didn't give James the option to run.

So it was a pretty specific set of circumstances - not an impossible one, but considering how small the magical community is and how few people are committing murder, a pretty rare one.  The odds that it happened a few hundred years ago and that it wasn't recorded thoroughly is probably pretty likely.  Harry's just the most recent and obvious case, so he's the only one that's known and understood.