Weight lifting for men?

howe much weight would be reccomended for a guy who's 5"11 and has a medium sized frame... he's 16 right now... they say you should only lift 2/3 of your body weight if he were to pick up his girlfriend who's 130 pounds would that be too much for him... cuz thats MORE than 2/3 of his body weight... btw is it different when your bench pressing weights, and when your just picking someone up?