Ruling on the daughters of a brother through breastfeeding

This is a message we received from its sender, Muhammad ibn Ali Salman, who says: To the honorable General President of the Departments of Scientific Research, Ifta, Da'wah, and Guidance, His Eminence Shaykh Abd al-Aziz ibn Abd Allah ibn Baz, may peace and the mercy and blessings of Allah be upon you. The subject: May Allah reward you for your good deeds, for clarifying good and eradicating evil and its signs. I am Muhammad ibn Ali Salman al-Ahmad al-Maliki from the district of Bani Malik, which is part of Jizan. May Allah reward you with the best reward for your good deeds and their clarification, and for eradicating evil and its signs. I have a brother through breastfeeding, and he has three daughters: Ma'iziyah bint Hasan, Fatimah bint Hasan, and Jamilah bint Hasan ibn Salim ibn Qasim. My aforementioned brother died before his father, and we became the residuary male heirs. Are these daughters mahram to me, and is it permissible for them to have a mahram or not? Please issue a ruling on this matter, may Allah guide you and keep your steps firm through His protection and care. We request that you kindly broadcast this fatwa on the program Nur 'ala al-Darb. May Allah protect you?
Answer: If the questioner's brother was breastfed by the questioner's mother five times or more, or if the questioner was breastfed by the mother of Hasan, this is the case. If he was breastfed by her mother five times or more, then he becomes his brother, and his daughters become daughters of a brother through breastfeeding, who are mahram. If this is established, meaning if the questioner's mother breastfed the aforementioned Hasan, then he becomes his brother through breastfeeding. Or if his father's wife breastfed the aforementioned Hasan five times or more, or if Hasan's mother breastfed the questioner five times or more, then the questioner becomes a brother to this Hasan, and an uncle to his daughters and an uncle to his granddaughters, and so on. He becomes an uncle, and he is their uncle through breastfeeding, and he is a mahram for them; due to the saying of the Prophet (peace and blessings be upon him): .
As for if the breastfeedings were less than five, or if there is doubt regarding the breastfeedings, such that it is not known whether he was breastfed or not, and it is only said that he is his brother through breastfeeding without certainty, then they are not mahram for the questioner, and he does not become their uncle except through established breastfeeding, by the testimony of a trustworthy wet nurse or the testimony of other trustworthy people that Hasan's mother breastfed him, or that his mother breastfed Hasan, so he became his brother, or his father's wife, or Hasan's father's wife breastfed him. This is the ruling in this issue.
Therefore, it is obligatory to be certain in the matter, so that if the breastfeeding is established, he becomes an uncle to the daughters of the aforementioned Hasan, and likewise to their daughters and the daughters of their children; he is their uncle.