From your description, it sounds like your intentions are good. But odds are this will ultimately blow up.

Brother MUST see the IRA (Roth or Traditional) as a tax-deferred savings plan that will help to provide for his financial needs in retirement. If he does not see, or understand, or care to understand this relationship, then all of what is being done for him will be lost. The odds are that when Brother knows this IRA is his, he'll want the money NOW (taxes be damed), which will be upsetting to 'A' who went through the trouble to set this up for him. Brother will quickly spend the money on some vice(s), further upsetting A.

Only people can own IRAs. Trusts can be beneficiaries, providing they meet certain pass-through requirements. I've read of some obscure way of directing mandatory inherited IRA distributions to spend-thrift trusts, but I have no idea if this would be possible with a competent adult IRA owner....I doubt it would.

IRA values of up to $1MM are excluded from one's Federal bankruptcy estate, but if the person does not qualify under Federal bankruptcy rules, the state may allow creditor judgements to claim IRA assets. But this varies by state.

BruceM