Ok...This is something I can really relate to!!! I don’t know if this will help, but it helped my sister, so I’m going to share.
She was almost very similar to your brother. I saw once come home from what was supposed to be an amazing day with friends, utterly upset and dragging her feet and look like her mind had shot off into space and ended up in another universe.
It was saddening to see, it made my heart drop, cause I love my sister way to much to see her like that. So I decided to talk to her, ask her how it went. She didn’t open up to me about it, she just didn’t want to say anything at all about it. So I let her stay quiet about it. I didn’t want to force her to open up in any capacity so instead, I just listened to whatever else she had to say.
But that’s what was the key here. I let her talk and talk and talk about whatever she wanted to, never trying to force a subject or pry into her mind. I did that to give her comfort, but to also let her know that I am there to listen to anything she has to say and that she can trust me to listen.
Eventually she did open up about it, and it was very discouraging to hear what happened. Most of her friends abandoned her that day, gossiped about her behind her back, and even had the audacity to tease her about being a depressing person to be around.
Honestly, my over protective nature of my sister, I almost had a big brother complex at what I had heard. I wanted to let those brats have it so bad...but it’s not my battle, it’s hers. And as much as I wanted to do something about it, it wouldn’t help her in the end.
So instead, I continued to listen to her and give her whatever support she needed. Never saying she needed to do ‘this’ or do ‘that’ to fix her problem. Instead offering a prospective and letting her mind do the solving for itself. I gave some advice sure, but what she needed more was for someone to just let her lash out on, a punching bag if you will.
Eventually she realized those people were poison to her; and she let them go as friends. She hates doing that, but she knew she had to. And she was much better off for it cause it gave her more focus on the people who ‘actually’ were her friends. And now she’s happier for it, I feel we both have a stronger relationship with each other as siblings.
Even if this doesn’t help you in your case, maybe it gives you some kind of idea. Just being there sometimes is also they need, someone that will listen to them. Offer encouragement, but don’t force your opinions on them of what they should or shouldn’t do. Give them a blank slate to paint their feelings on and help them to unravel their own thoughts. It might help. I hope it works out for the both of you. Good luck mate.