Kids smoking marijuana... what to do? i am 26 years old and have a younger cousin who is 14 who is smoking?

weed and just found out he's having . now when i was in junior high and through out high school i smoked weed here and there, but it never affected me school-wise. my cousin has always had a hard time with school (paying attention, and submitting his hw). he's very smart and can play the piano by ear, he just seems to lack motivation. his parents are sooo irritated with his behavior. they've gotten him a tutor, grounded him, took away all kinds of possessions, but it doesn't do anything. his behavior doesn't change. what can you do in this situation? i feel like i should tell my auntie about what he's doing but also feel like it's just adolescence and about 75% of all high schoolers have smoked weed. i'm cooking and was watching my son sleeping on the monitor and thought to myself "geez, i'd want to know if my kid were smoking weed." i'd actually probably drug test him once he's in junior high and high school... as wrong as it sounds. what would you all do? would you want to know?