Who is an executor has *nothing* to do with who inherits what under a will or otherwise. The executor is primarily an administrative position, for which there is usually some compensation allowed. The executor cannot determine who does or does not receive from an estate; one does not need to be an executor to receive; and declining acting as an executor does not affect what one receives. Heirs will receive whatever portion of or assets from the estate the will (if any) indicates they should receive; and if there is no will, they receive the share determined by state law for "intestate succession": no more and no less. If there was a will and it said by its very terms that "my son shall not inherit if he does not act to administer my estate," that would be one thing; but absent language as specific as that in a valid will, your brother's decision does not affect whatever he would receive.