Breastfeeding is specific to the infant

Question: Two married sisters: the first has several children, and the second does as well. The first nursed her sister’s daughter with many full feedings, and the second nursed her sister’s son with many full feedings. What is the resulting prohibition between the sons and daughters of these two sisters?

Answer: Breastfeeding is specific to the infant, not his siblings. Thus, he becomes the son of the woman who nursed him and her husband, and a brother to her children, both male and female, but not to his siblings who were not nursed by her. They do not become her children because she nursed their brother, as the Prophet (peace and blessings be upon him) said: .
It is necessary that the breastfeeding be five feedings or more, while the child is within the first two years; as the Prophet (peace and blessings be upon him) said: , and as he (peace and blessings be upon him) said: , and as Aisha (may Allah be pleased with her) said: “It was among what was revealed in the Qur’an that ten known feedings establish prohibition, then this was abrogated by five known feedings. The Prophet (peace and blessings be upon him) passed away while the matter remained as such.” This was narrated by Muslim in his Sahih, and by al-Tirmidhi in his Jami', and this is his wording. And success is from Allah.