The ruling on a man who has two wives and whose child was breastfed by one of them, and who wishes to marry the daughters of the second wife

This is a letter we received from Shaykh Hamdan Hamid Mas'ud al-'Uzli. In his letter, he says regarding breastfeeding: A man married two women and had daughters from both of them. There was another man, distant from them, who also married a woman. His wife gave birth and left behind a child, so he brought the child to the first man to be breastfed along with his daughters. In fact, he gave the child to the first wife, and she breastfed him along with her daughters. The question is: Does this son have the right to marry the daughters of the second woman, with whom the child was not breastfed? Please inform us, may Allah reward you, as we are confused about this matter. May Allah guide you and set your steps aright?
Answer: If this child was breastfed by one of the two wives five times or more, he becomes the son of the man... the husband of the two women. He becomes his son, and all of the man's children become his siblings. If he was breastfed by one of the two wives five times, five breastfeedings or more, then by this he becomes his child. The wife who breastfed him becomes his mother through breastfeeding, and the second wife becomes his stepmother through breastfeeding. All the children of the two wives become his siblings through breastfeeding. Therefore, he is not permitted to marry the daughters of this one or the daughters of that one. Likewise, all the children of this husband from all women, before and after, become his siblings. Likewise, the daughters of the two wives; the daughters of the wife who breastfed him are his siblings... his sisters, and he is not permitted to marry any of them. As for the second wife who did not breastfeed him, if she has daughters from another husband, daughters from a previous marriage before this husband, there is no harm; they are not his sisters. But if her daughters are from this husband, they are his siblings; because he has become the son of this husband through breastfeeding. Therefore, all the children of this man are his siblings, both male and female, if the breastfeeding is five times... five breastfeedings or more within the two-year period, while the child is within the two-year period. If the breastfeeding is less than five breastfeedings, such as one or two, no, it does not have the ruling of breastfeeding. It does not establish the prohibition, nor is it considered; due to the saying of the Prophet (peace and blessings be upon him): , and the hadith of Aisha (may Allah be pleased with her) in Muslim: So it is necessary that there be five breastfeedings or more...