How should I deal with my groupmate's unprofessional behavior as a TA? I have a colleague in my group who became TA for a course which we took together, which is taught by our mutual advisor. It is almost a policy that a student can't become TA unless he scores an A in the course, but he was chosen because he asked "first" and the professor is "nice", even though I was the highest scoring student, which usually gets the teaching assistantship. He also knew that I wanted to TA that course, yet he still asked.

Many students come to him for questions or help. He usually tells them to copy the homework (!) or to ask me or a colleague of mine for help because "he doesn't know and [me and my colleague] know the material much better!"

How do I deal with such a person? I mean, my colleague and I try to answer all the questions the students have, but the annoying thing is that we can't be doing half the job while he gets all the money. We spend our time trying to help others where he should do that. We are very busy people and we don't have time for this when we don't have to officially do it.

Should I talk to my advisor about this? I don't want to sound as if I'm envious.
Being nice is nice, but you also need to set your own priorities. You are not the TA for that course, so you are not obliged to answer any questions. If you happen to have time and feel like answering a question (notice the singular), then fine, answer it. When not, just politely say you don't have time and that they should go see the TA. Also, you are not responsible for (bad) advice given by that TA. Instead I would focus on getting your own research done, or do the TAing of some other course.