Question: I breast-fed my husband’s brother for almost two and a half months along with my eldest son. I have many children, and my husband also has many brothers. Do my children and their paternal uncles thereby become milk-siblings? My husband’s brothers have daughters as well—do those girls become forbidden to my sons? Be aware that the brother I nursed, together with his elder brothers, do not share the same mother; each has a different mother.

Answer: The brother of your husband whom you nursed becomes your son through breastfeeding and thus a milk-brother to all of your children, male and female alike, provided the nursing took place within the first two years of his life and reached five or more separate nursing sessions. Consequently, he is your milk-son and a brother to every one of your children, whether born before him or after him. His own sons, therefore, may not marry the daughters of their paternal uncle—your husband—because he himself has become their paternal uncle through breastfeeding.

As for the rest of his brothers, the breastfeeding has no effect on them. They may marry their cousins’ daughters as they wish, for they have no connection to the nursing that occurred between you and one of them. The ruling applies exclusively to the nursling himself and to his descendants. Allah, Exalted and Most Knowing, knows best.

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The breastfeeding ruling pertains to the nursling

Question: I have a maternal aunt who has both sons and daughters. One of her daughters nursed from my mother together with my elder brother. Does that girl become our milk-sister, and is it permissible for us to marry her younger sister? Kindly advise us, and may Allah reward you.

Answer: The girl who nursed from your mother is indeed a milk-sister to all of you. Her other sisters, however, are unaffected by that breastfeeding, so there is no objection to your marrying any of them. They did not nurse from your mother, and you did not nurse from theirs.