I think your parents had it right when they scheduled a counseling appointment for him. You said they did not want him to take medication. Going to counseling does not mean that he will have to take medication. Some counselors suggest medication as do some psychiatrists. Because it is suggested doesn’t mean he has to take the medication. He has a choice in the matter. Your parents or your brother could simply tell the counselor he is very sensitive to medication and that he is strictly interested in psychotherapy.
You’ve expressed many concerns about your brother and I’m wondering if you shared that information with him. Does he know how worried you are about him? Have you approached him about your concerns? Has anyone approached him? He doesn’t seem very receptive to your parents at this point but he may be open to talking to you. You should talk to your brother and be honest about your concerns. In talking with him you can express the importance of getting help. You could even make the offer that you’d be willing to attend therapy with him, or at least be part of the process in some capacity. This might include you driving him to his therapy sessions or participating in several if he’d be open to it.
If none of these suggestions work then you and your family should come together to create a plan about how to approach this problem. A family therapist may be very helpful with this process. This means that even if your brother is not willing to attend treatment the family could see a therapist to receive guidance about this issue. Let me know how things turn out.