BROTHER'S DAY. Observed every year on May 24, Brother's Day honors the brothers in our lives. Whether we have one or many, our brothers hold a special. 2 May What is Brother and Sister day? Brother and Sister day is an event to mark and honour the life long bonds between brothers and sisters. National Brother Day seeks to celebrate brothers, the male sibling and their contributions to each and every one of their families. It seeks to celebrate the bond.