question regarding my mom's will

i am executor of my mother's estate. i am selling her property and need to divide the money between beneficiaries. her will states it should be divided between her children equally. then it states: provided that if any of these persons shall predecease me leaving issue surviving me the the share of such person would have received had he or she survived me shall pass to his or her issue in equal shares per stirpes and not per capita. i am not sure what this means. a brother passed after my mom, does this mean i give his portion to his children?