How can i stop getting jealous of my brother, and everyone else in the Army?

ok i'm only 15 and ive wanted to serve in the military my whole entire life. no joke. i would like an mos as a mechanic (i kno a lot about cars and could learn about humvees and stuff) or infantry. my brother just recently completed bct. he sent us pics of him in his acu, and i got really jealous. every time i hear about the army not the marines no branch except the army i get jealous and i say to myself, god in 2 years i sign up. the bad thing about this is i keep getting that thought in my head the army will have to much people by then and will stop recruiting people. i could care less about the benifits. so how do i stop getting jealous and do you people know for my two mos's that i want to qualify for, will i be able to join for any of those 2? thanks