Q: Two women breast-fed each other's children. Only one son of a woman and one daughter of the other woman were not breast-fed by other than their mothers.
Now the boy wants to marry the girl; she was not breast-fed by his mother and he was not breast-fed by hers.
Please submit my question to His Eminence, the Chairman of the Departments of Scholarly Research, Ifta', Da`wah, and Guidance. May Allah grant you success and safeguard you!
If the reality is as you mentioned, it is permissible for the boy and the girl, who were not breast-fed by each other's mothers, to get married. The fact that the siblings of the girl were breast-fed by the mother of the boy does not affect their marriage.May Allah grant us success. May peace and blessings be upon our Prophet Muhammad, his family, and Companions.