my older brother is lazy what can i do?

i am 24 and i have an older brother who is 26. i also have another older brother and an older sister. my mom was a single parent to 4 kids and always worked her butt off to provide for us, now my 26 year old brother is completely lazy! he has two kids and a wife but flat out refuses to work or go to school and every month i find myself paying for more than half of their rent< everybody tells me that i should stop helping him but if i stop helping im worried about my niece and nephew, its not their fault he wont get off his butt. he smokes weed all day and plays video games all night. i would do almost anything to get him into shape and on his feet! i joined the army at 17 and have worked for everything i have so it frustrates me to see him doing nothing with himself. we grew up seeing my mom with a strong work ethic so in turn i think i picked up on it. but somehow it skipped one of my brothers... lol it sounds crazy but hes a 26 yr old guy and doesn't want to work almost anywhere. i had a really good job lined up for him making 17 an hr and he wouldn't quit smoking weed for it!! he doesn't want to work i the heat or doesn't wan to work doing manual labor and when i asked him what he wanted to do with his life (no lie) he told me he wanted to be a race car driver....smh.... i told him to grow up. i want to be a pimp from oakland or an astronaut but its not halloween! im at a loss on what to do. i told him i would buy him a car or books or whatever he needed if he would go to school or get a job. and he wont. he has an excuse for everything. even with two kids and a wife he wont step up... and his wife lets him because she doesn't want to start a fight!! he said he wants to work at subway cause he can be in the AC and make himself food! please help with any advice!! for some reason it stresses me out... i try to figure out more ways to help him more than i do on my own problems... i guess i just want to see him happy and successful. my mom always tells me "you can lead a horse to water but you cant make him drink" and its so true lol i could put the world in front of him and he'll figure out a way to break up weed on it....