<human>: I'm a 20 year old physics and mathematics major at a big university, and need to know if I'm being too hard on my (half) brother, or if he really does need to change (and advice on how I can help).

*What makes me think he might be a douchebag*: he recently intentionally got himself fired from his technical support/telemarketing job so he could siphon unemployment funds for as long as possible before having to find a new job, and has moved back in with our grandparents to cut down on expenditures. He's 30. His cutback in expenditures doesn't include quitting smoking (cigarettes), or considering stopping buying/smoking lots of marijuana (upstairs in guess who's house). He once claimed he needed it to function properly. This is the second or third time he has done this in the last 6 or 7 years. My grandparents are amazing people who worked hard their entire lives to have what they did (but are very old/disabled now), and I'm not comfortable with him doing things like this in their home.

The problem is, I have to go back to visit (the parents/grandparents live hundreds of miles away from me, in the same neighborhood) since I didn't get an internship/summer REU this break. For one, I don't want his (in my eyes) bad behavior/work ethic (he almost always complains about something rather than trying to change it) to rub off on me, and don't know how I can help him/my family in this situation. I hope you can give me some advice!

Summarize the given text in a few sentences.
<bot>: I think my brother is negatively affecting my family and I don't know how to (or if I should try to) change it.