Baby weight for a breastfeeding baby

Hello mga moms..normal lang po ba ang weight ni baby for 8months ay 8kls?im wondering po kc if sapat o hinde yung nabibigay kong milk sakanya..in case of her cousins po kase na halos kasing age nya is talagang almost na yung weight nila sakanya..advice naman po para mapataba ko po si baby..thank you#pleasehelp