When there are 3 executors to an estate but 1 of them declines to accept his portion of the executors’ fee, are the other 2 executors legally entitled to his share?

Executor's fees are set by statute in New York and how they are divided will depend on a few factors, namely the value of the estate subject to the executor's fee and how many executors there are.  Arguably here there are two executors if one has renounced his fee.  So you can not calculate the fee by three and then split his portion.  You must calculate the fee as if there are only two executors.  This distinction matters depending on the size of the estate. For example, if an estate is valued at $100,000 or more but less than $300,000 each fiduciary is entitled to the full fee allowed to a sole fiduciary unless there are more than 2 fiduciaries in which case the full fee allowed to 2 fiduciaries must be divided among them according to the services rendered by them respectively or unless the fiduciaries have otherwise agreed in writing between or among themselves. But if the estate is valued at less than $100,000 where there is more than 1 executor the full fee / commission allowed to a single executor must be divided among all of the executors according to the services rendered by them respectively. And the court can always modify the fee. Your attorney needs to help.