100% to me so each sibling's share is the same, 0%?!
You are so wise in asking around, being in tune with your emotions, and educating yourself. I think that joint sibling-professional trustees and broad discretion is ideal if you go the trust route. The professional only need be involved for amounts over $X. State generally that the trust cannot be used to further AS' addiction, but don't micromanage it beyond that. There are too many factors. Just look at what people say they do and don't do about their loved ones' addictions here on SR! You either have wise trustees or you don't. That's the key.