My brother is a slacker! I'm worried about him! Please Answer!?

All he does is sit around and play on the computer. he's always skipping his us history cl and i'm worried he's not gonna get into a good college! how do i convince him that he needs to work harder? He's 17 and hasn't applied for a SINGLE college! I'm a 14 YEAR OLD girl and i care more about his future than he does!! I'm worried about him, like i said. Am i being too overbearing, and is it too much to ask of him to just apply for one college? What do i do? i don't want him to fail at life...? how do i get him to see that he needs to care more? Im worried sick about him!!! Am i taking on too much?