Question regarding how to handle a $20,000 gift

My husbands grandmother was put in a nursing home and since her children were on the deed they decided to sell the house and they would split the proceeds evenly. However, my husbands father (his grandmas son) is deceased and his grandmas will states (even though she is still alive) that his fathers portion should be split between his children (my husband and his sister). This occurred but the money was given to my husbands mother first and then she wrote out a $20,000 check for my husband and his sister. How does this impact my federal and state tax returns?