Forbidding a man who suckled from one's wife's grandmother from entering upon one's wife, who is his niece by breastfeeding

Q: My second wife has a maternal uncle, who is older than her. When my wife's maternal uncle was an infant, another baby received more than five times of breastfeeding during the first two years of his life from the same breastfeeding woman. It is known that my wife's maternal uncle and this other man are (Part No. 21; Page No. 87) siblings by breastfeeding. I am asking whether this man - who was breast-fed with my wife's uncle - is considered the brother of my mother-in-law by breastfeeding or not. In other words, is he considered my wife's maternal uncle? If the answer is yes, I want to pose another important question, which is:Do I have the right to prevent him from greeting and visiting my wife? Would I be sinful if I prevent him from entering my house? It is worth mentioning that he has weak Iman (Faith), he is negligent of performing Salah (Prayer), and he smokes; and I do not feel that my family is safe in his presence, especially that I have another wife and adult daughters. Do I have the right to prevent him from greeting my family and entering my house? Would I be sinful if I do this? Please advise. May Allah reward you!

A: If the mentioned breastfeeding is confirmed to have taken place five times or more during the man's first two years of life and if the woman who breast-fed him was the mother of your mother-in-law or a stepmother of your mother-in-law, the breastfed child is, thus, a brother of your mother-in-law by breastfeeding and a maternal uncle of your wife. Accordingly, he is a Mahram (an unmarriageable relative) for your wife. If you fear that his entry to your house might cause harm to your family, you should prevent him in order to ward off corruption.May Allah grant us success. May peace and blessings be upon our Prophet Muhammad, his family, and Companions.