What is the legal ruling and what must a married man with children do if an elderly woman, who is his wife's sister, tells him that she breastfed him for four days in his infancy, and he believes her?

Jurists have differed concerning the acceptance of a single woman's testimony regarding suckling. The majority of jurists do not accept it, while the Hanbalis dissented, accepting the testimony of the nursing woman. They based their reasoning on the Hadith of Uqbah ibn Al-Harith, who married a woman, and then a black maidservant came and said that she had suckled both of them. The Prophet, peace and blessings be upon him, then commanded him to separate from her. Accordingly, the man must separate from the woman and annul the marriage, and the children remain with him due to the شبهة (doubt/semblance) of the marriage.