Ah yes, Jade Empire, my least favorite of Bioware games. It's still one hell of a game, but be prepared for a relatively shallow and easy combat system, and a game that ends long before it should. (It's only 15-20 hours long). Still though, I've had enough fun with that one to play it through several times.
You're 16 and your mom won't let you buy an M rated game? Man, that sucks.
Trust me, this is incredibly mild for an M rated game. The main combat is actually completely bloodless. The only reason it got an M rating is the cutscenes can sometimes be pretty blood, and your enemies gush blood, if you take them down using something called a harmonic combo. Other than that though, there's absolutely on reason for this one to have an M rating.
Yep, Mass Effect's another great one from them. If you liked Kotor, and Jade Empire, I'm sure you'll like Mass Effect (although, there was more of a focus on combat in Mass Effect than the other two).