Who gets the minerals

Just curious my father signed for mineral rights that was sold by my grandmother. He passed and I know me and my sister share a third with my stepmother. Just curious what happens when my stepmother passes. Does it revert back to me and my sister after she passes or can she will it to her kids? In mississippi

I’m not licensed to practice in Mississippi, but the following may be helpful. https://law.justia.com/codes/mississippi/2010/title-91/1/91-1-3/