Why is he doing this? All of his negative energy is driving my parents mad! ?

Finished high school about two months ago but missed graduation (didn't feel like going). Told my parents that I graduated and that I missed the deadline (sadly). I have to pick up the diploma myself on August 17th (school is closed). I've noticed the loser (half-brother) that's been working a low-paying job at AutoZone since he graduated high school (which was six years ago) pestering my parents asking them for my diploma and questioning whether I really did graduate or not. Telling my parents that I'm not gonna achieve anything in life if I don't find a job (he does this while I'm not around). My parents are getting a bit suspicious asking me when I'm getting my diploma and I say the same thing over and over. They're even acting a bit less upbeat and talkative. But I just smile and lay on the bed and watch my favorite shows on television when he comes around (it pisses him off). I think he has to cling off my and live his own life. Why the hell is he doing this? Does it bother him that I'm living for free while he's been working for six years with nothing but liabilities, debt, and only one thousand in the bank? Haha. People you gotta help me out on this one