let the kid chase his dream

i think this is the best way to tell him.

"for now my little bro, u need to concentrate on your engineering study first", get a hold of your degree first.
then when u get your degree, it's up to you which direction u wanted to go.

u know when he ended up his degree program, he would think twice to be in the music education or not.

good for you.
just make sure u assist him in doing music as his part time as long as he is serious about it.
if he really serious of something he dream of then he deserve it.