My mother breastfed my aunt’s daughter, while my aunt breastfed one of my male brothers

The questioner : My mother breastfed my aunt’s daughter, while my aunt breastfed one of my male brothers. Is it permissible for us, who were not breastfed by my aunt, to marry my aunt’s daughters? And likewise, is it permissible for my aunt’s sons, who were not breastfed by my mother, to marry our sisters? Or are we, our brothers, and my aunt’s daughters considered siblings through breastfeeding, such that we have no right to marry one another? We ask for guidance on this matter.

The Shaykh : Breastfeeding establishes prohibition just as blood relations do. The Prophet (peace and blessings be upon him) said: The prohibition extends to the breastfed child and his descendants, but it does not extend to those in his generation, such as brothers and sisters. Based on this principle, we say: As for your aunt’s daughter who was breastfed by your mother, it is not permissible for any of you to marry her, because she has become your sister through breastfeeding. As for your brother who was breastfed by your aunt, it is not permissible for him to marry any of his aunt’s daughters, because he has become their brother through breastfeeding. Beyond that, there is no prohibition. It is permissible for you to marry your aunt’s daughters who were not breastfed by your mother, and it is likewise permissible for your aunt’s sons to marry your sisters. This is because the Prophet (peace and blessings be upon him) said: There is no bond between you in the situation we have described.
I repeat: Your aunt’s daughter who was breastfed by your mother has become your sister, so it is not permissible for you to marry her. And your brother who was breastfed by your aunt has become the brother of her children, so it is not permissible for him to marry any of her daughters. Beyond that, intermarriage between you is permissible. It is permissible for you to take wives from your aunt’s daughters, and it is permissible for your aunt’s sons to take wives from your sisters.
However, we must know that breastfeeding has no effect unless it is five breastfeedings or more, and occurs before weaning within the first two years. If it is less than five breastfeedings, it has no effect. If a child is breastfed by a woman four times, he does not become her son. If he is breastfed five times or more after weaning, after the two-year period, his breastfeeding has no effect. The evidence for this is the hadith of Aisha (may Allah be pleased with her), narrated by Muslim: , and his saying (peace and blessings be upon him): There is no consideration given to satiety or lack thereof. If a child is breastfed five times, even without becoming satiated each time, he becomes the son of the woman who breastfed him. If he is breastfed once and becomes satiated, it is only counted as one time, even if he became satiated. The criterion is the number of distinct breastfeedings, and there is no consideration given to satiety or lack thereof.
On this occasion, I would like to point out an important matter: the wet nurse should be diligent in counting and recording those she has breastfed, so that the matter is not forgotten by her or by others. Many questions arise involving doubt about the number of breastfeedings, or about the breastfed child, or even about the wet nurse herself, due to a lack of recording and control.

The questioner : May Allah bless you, Shaykh Muhammad, and may He magnify your reward for what you have presented to us and to the honorable brothers and listeners.
Our honorable listeners, our guest in this session was the honorable Shaykh Muhammad ibn Salih al-Uthaymeen, professor at the College of Sharia in Qassim, and preacher and imam of the Grand Mosque in the city of Unaizah. We thank you for your good attention and hope to meet again tomorrow, may you and we be in good health and well-being, by the permission of Allah the Exalted.
Now we leave you in the care and protection of Allah, and may the peace of Allah and His mercy and blessings be upon you.