Ira beneficiary vs. terms of a trust?

A LOT depends on the the wording of the trust and in your case it may also depend on the circumstances on which the trust was filed. You are not going to get a definitive answer here. You need your own attorney.

I believe it comes down to who was the owner of the IRA at the time of death. Was it your brother or was it the trust? If it was your brother, the beneficiary should stand as you. If it was the trust, then technically the trust still owns it and the terms of the trust and the trustees can decide who the money goes to.

If this was all done the day before he died, then his state of mind can be questioned and whether he really understood what he was signing (but that will probably be a court issue).

As an estates & trusts paralegal, I'd be interested to know if that Trust was actually funded by the IRA. Since you've already collected on it, it seems to me that no-one in the IRA administration department knew of this magical Trust, thus the Trust was a shell game. Moreover, it could likely be a case of pressuring your deceased brother on his sickbed...was the Trust validly witnessed?

Regardless, I highly recommend consulting an attorney who practices probate law, including trust admin, and handles litigation.

Consult a lawyer, it doesn't work that way.