Damn that must have been frustrating, I can't recall any major problems with my parents (though I'm sure there's been a few) but one vivid incident I recall happened with my little brother. On my first playthrough on FFX I was about half way through the story, and just getting to the exciting bit (just after you go to Bevelle) when my brother took a interest in the game. He started his own file and while I was watching saved directly over my save file, simply because it was the first slot the cursor came over, it was an easy mistake. I did it too a friend's file once (though he was only a few hours in and barely ever touched the game again) but it pissed me off to no end at the time, over 30 hours of gameplay lost just like that.