What should my younger brother do in my wedding?

I think that ten is okay for a ring bearer and you can certainly have two ring bearers. Also, he could hand out programs, or be a junior groomsman.

My brother (who is also special needs) will be handing out programs. That way he can be involved but the stakes are low and my parents don't have to worry about getting him a suit or anything.

Is there someone he could share a duty with so whatever you choose won't be so overwhelming?

He could be one of your attendants (a "bridesman"). That would require him only to walk to the front with the bridesmaids.

I have seen other suggestions like carrying a banner in front of you that says "Here Comes the Bride", doing a reading, or saying a poem.

Is there a unity candle or something he could bring to the alter?

He could hand out programs, I just don't want him to feel completely left out since both of my other brothers are in the ceremony. I hadn't thought of junior BM/GM for my wedding, he could do that as long as he is able to sit down in the first row after walking down the aisle.

We won't be having a unity candle & he has a speech impediment so a reading wouldn't work out very well. But I was thinking maybe he could walk with my flower girls & ring bearer since they will all be younger than him & he usually likes to be "in charge" of little ones who look up to him. Would that be too weird for him to be like the "attendant" for that?