Ruling on marrying one's paternal cousin's daughter if the husband was breastfed by his paternal grandmother

The listener Muhammad Nour, a Pakistani from Pakistan working in the Kingdom, sent a message saying: A man was breastfed by his grandmother along with her son, and he was one year old at the time (meaning: he was of the age of breastfeeding). This breastfeeding continued for one year. After that, he married his paternal cousin's daughter. Did this man become his paternal uncle's brother through breastfeeding or not? And if he became his paternal uncle's brother, is it permissible for him to marry his paternal cousin's daughter? Some scholars issued a ruling that this marriage is invalid, and then one of them issued a ruling that this marriage is valid. It is known that he has four or five children from his paternal cousin's daughter. I ask for your guidance: Is this marriage valid or not? And if it is not valid, what are the consequences of that, and what is the status of the children? Please inform us, may Allah reward you with good.
Answer: If the breastfeeding is established by the grandmother's admission and she is trustworthy, or by the testimony of some trustworthy people that she breastfed him five times or more, even if it was less than a year, five times or more is sufficient, then he becomes her son and becomes his father's brother if his father's mother breastfed him, and he becomes his paternal uncles' brother, and his paternal cousin's daughter becomes his brother's daughter, and he is not permitted to marry her; because the paternal uncle became his brother and the father became his brother, so the marriage with his paternal cousin's daughter is invalid; because she is his brother's daughter through breastfeeding.
And it is established from the Messenger of Allah (peace and blessings be upon him) that it was said to him: .
The summary is: This man who married his paternal cousin's daughter, and the breastfeeding from his grandmother is established, his marriage is invalid, and his children follow him due to the doubt of the marriage in which they erred. His children are attributed to him, and praise be to Allah, but it is obligatory for him to separate from her and not have contact with her, and to establish that in the court so that she may marry whom she wishes after the waiting period, if the breastfeeding is established by the woman's admission and she is trustworthy, meaning the grandmother, or by a trustworthy witness or a trustworthy woman who knows that and is precise that she breastfed him for a year or less than that, and what is required is five breastfeedings. Whenever she breastfed him five breastfeedings or more, it is sufficient, by the saying of the Prophet (peace and blessings be upon him) to the wife of Abu Hudhayfah: , and she is Sahlah bint Sahl ibn 'Amr, and he said to her: .
And in Sahih Muslim, from 'A'ishah (may Allah be pleased with her), she said: , and in a narration of al-Tirmidhi (may Allah have mercy on him): .
This indicates that five are sufficient by the saying of 'A'ishah (may Allah be pleased with her): , meaning: five were accepted instead of ten , meaning: and the practice is to accept five, and in a narration of Muslim: meaning: its wording was abrogated and its ruling remained.
So what is obligatory for this man, as long as his breastfeeding is established, is to separate from his paternal cousin's daughter; because she became his brother's daughter, and his children from her follow him due to the doubt of the marriage, and we ask Allah to replace each of them with something better than their partner, and to guide everyone to what pleases Him, and if he did not intend it but did it out of ignorance, we ask Allah to forgive them both.
The presenter: O Allah, amen, may Allah reward you with good.