My 5 minor sons were beneficiaries of my aunt's estate. Part of the estate was a $157K IRA. She had begun taking her RMD. The beneficiary of the IRA was her trust. Then the 5 boys split the trust. My questions is how is that taxed? Does the trust (or estate) pay tax on the distribution or do the individual minors?

The IRA will report the distributions they make to the trust, and so the IRS will expect the trust to report it and pay taxes. But if the trust then distributes all its income to the heirs it becomes taxable to them, and the trust will have to issue schedule K-1's to document this.

Naming a trust as your IRA beneficiary is typically done for estates that have significant assets (enough to use such a strategy to avoid estate taxes). The trust must be set up following some pretty rigid rules as "see through" or "conduit" trusts. I assume your aunt had the assistance of a CPA and/or attorney in doing this - I'm sure they can help you with how to handle and report taxes due.