RMDs for Inherited IRA’s

As I mentioned under another topic I have a Trust with an Inherited IRA in the main Trust which I use for 2 of the Beneficiaries and 2 other Beneficiaries have their own Inherited IRA’s in Sub Trusts under the main Trust. The oldest Beneficiary, age 89, is in one of the Sub Trusts. Since she is the oldest, as long as I use her age and take the RMD amount for all the other Inherited IRA’s combined can I forgo the RMD for her Sub Trust? Thanks!