Only a single save for your main character on a game which you may spend hundreds of hours playing is risky, risky, risky.
They say on a long enough timescale the survival rate for everyone drops top zero... this holds true for TES character saves too imo.
The longer you play, the narrower the odds that something will happen to your save... that's cold hard maths my friend.
Make semi-regular backups at points in your game you're happy to rollback to if something goes awry... because you just never know... little brothers, power outtages, alien emps, AI virus taking over all internet connected gaming devices... you just never know.

Best thing you can do now OP is sit your little brother down and play together on a new shared character and teach him to respect, value and take care of saves.