There's quite a bit about that which doesn't make much sense. I believe Spock (senior) stated in the reboot films that said supernova [would have] destroyed the galaxy, when that just wouldn't have been possible. No supernova (from a dying star) is that powerful.
For what it's worth, I do agree with you though, Nero could have simply lost his wife and family to a supernova that Spock didn't prevent in time, one that took out (a) solar system (as they're more likely to do). We know it wasn't the Romulus sun that went nova, cause you can bet Romulan scientists would have noticed. Somehow another sun/star exploded and reached their system (not impossible, just convenient). I guess Abrams wanted that wow factor, but it has allowed for some interesting novels and gameplay elements (thinking STO).