Does the sister's daughter become a sibling to the questioner's children through رضاعة (breastfeeding) from his wife?

There is no difference between a baby suckling from the breast or drinking milk that has been expressed. For prohibition to be established, five distinct feeding sessions are required. Moreover, according to the majority of scholars, breastfeeding has no effect if it occurs after the completion of two years of age. So, if the infant is two years and six months old, breastfeeding has no effect on establishing prohibition whatsoever. However, if the infant has not exceeded two years of age, prohibition is not established except with five feeding sessions.