Encourage his present guardian(is that you?) to send him to some counseling. You are BOTH grieving! No two people grieve the same way. There are things you can talk with a therapist about that you could never tell a family member no matter how close you might be.
I know. My wife and I lost a son last year. May 29th will be the 1st anniversary.
You can continue to be there for your brother, but there are certain things that he will never say to you. This is normal, but he still needs to talk about these things. A therapist can be just the thing.
My wife would have committed suicide 3 times by now at least if she hadn't been able to talk to a professional. Yes they can be expensive if you don't have insurance coverage, but the cost is well worth it.
I feel some of your pain, but only you know what you are feeling. I would recommend that YOU also go see a therapist for a while. You have been put through a lot at a young age. YOU need to talk too.
BTW, I not only had to plan my son's funeral, our conductor bailed without so much as a last minute phone call. I had to conduct the ceremony on zero notice. I was the only one who could. I did the best I was able, but I'm afraid it was a poor job in the end.
In a way, I wish I could do it over so that I could do and say things differently, but the pain of doing so would kill me(or I would kill myself).
I guess it's better to leave that alone and let history be what it is. Two days after the funeral, my wife told me she wanted to hit the next person who told her they were "sorry".
I miss him SSSOOOOOO much!!!!!!!!!
My heart is saddened for you and your brother.