Ruling on a person told about his breastfeeding from another woman without knowing the number

Q: We have a daughter who was breastfed with one of her paternal cousins. We discovered this from her maternal uncle who mentioned that this took place twenty-four years ago. Now this paternal cousin wants to marry her. Neither her father nor her siblings know anything about this suckling. Moreover, her maternal uncle does not know how many times her uncle's wife breastfed her, nor whether they were sufficing and satiating. Knowing this, we stopped the marriage and invited her maternal uncle and asked him: "Do you know about the number of breastfeeding?" Whereupon his reply was that he knew nothing about the number of breastfeeding. This led us to suspending the marriage.We hope Your Eminence will advise us, knowing that both mothers died. We hope to receive your answer on this question as soon as possible since their marriage depends on your reply. (Part No. 21; Page No. 39

A: The breastfeeding that prohibits marriage takes place only if the baby had five sucklings or more during the first two years. The description of one suckling is as follows: a baby holds a breast and sucks milk. If it leaves it to take a breath or to be moved to another breast, then this is to be counted as one breastfeeding, and so on until five times of breastfeeding are counted. If the number of breastfeeding is less than five, even four, then this breastfeeding does not prohibit marriage. Therefore, if this girl suckled five times or more from her cousin's mother breast, she is unlawful to him. Mentioning Mahrams (spouses or unmarriageable relatives), Allah (Exalted be He) says: Forbidden to you (for marriage) are: your mothers, your daughters to His saying: ...your foster milk suckling sisters and: The mothers shall give suck to their children for two whole years The Prophet (peace be upon him) said: Milk relationships are equal to blood relationships in rendering marriage unlawful, i.e. whatever prohibited due to blood relationships is also prohibited by milk relationships. (Agreed upon by Imams Al-Bukhari and Muslim). It was authentically reported that `Aishah (may Allah be pleased with her) said: "It was revealed in the Qur'an that ten clear sucklings prohibit marriage then it was abrogated (and substituted) by five clear sucklings, and Allah's Messenger (peace be upon him) died while it was likewise." On the other hand, if she had less than five times of suckling, if she was suckled after her first two years, or if her suckling is doubted, it is permissible for him to marry her. (Part No. 21; Page No. 40) May Allah grant us success. May peace and blessings be upon our Prophet, his family and Companions!