My sisters husband just passed away without a will, his mother passed approx 11 months before, he was the executer of her will. None of the accounts left to my brother in law had my sisters name on it. Will she lose his portion of the inheritance and revert back to her estate? And how does she claim a portion?

If I remember right his share goes to his wife.
I am pretty sure I do remember right.

Were there any children? Someone else will need to take over as executor of the mother's estate. His estate will be the beneficiary.