OldShooter
Give me a museum and I'll fill it. (Picasso) Give me a forum ...
To amplify a little now that I am at a real keyboard:This!
A very straightforward trust provision is called the "HEMS Standard." (You can google it and read until you doze off.) The trustee is directed to provide for the beneficiary's Health, Education, Maintenance, and Support. IOW to disburse what makes sense; part of the trustee's stewardship is to manage the money and the disbursements so that your brother doesn't run out of money.
An annuity is a poor tool for what you want to do because there is no flexibility. What if your brother ends up in a nursing home? IANAL but I think that annuity is an asset that must be spent before he gets any public support. Again, IANAL, but the trust is not your brother's asset so I don't think it gets automatically tapped. That's just one scenario and I may be wrong about the spend-down issue, but you can certainly think of others. What if he ends up on hospice for 6 months? The trustee can accelerate payments to make his end-of-life more comfortable while an annuity can't.
The trust can include other instructions, too, maybe about payments on his birthday, or whatever. The trust grantor can also specify what happens to the balance of the trust if the beneficiary dies. Charity? Family? ... whatever.
Finally, both Schwab and Vanguard are now advertising very inexpensive trust services. I would check those out before agreeing to pay big bank fees. I am sure that Fido, too, will enter that market if it has not already done so.