Life estate remainderman

My father died without a probated will and we inherited his mineral rights. My mother inherited 1/3 and the children split remaining 2/3. My mother sold her interest which resulted in a life estate. Three of my siblings sold their interest.

My mother passed in 2025 after siblings sold their initial interest. Are they not entitled to remainder share of mother’s interest? Or does it go to company that bought interest prior to her death.

Thank you.