Is it permissible to shake hands with the wife of one’s maternal uncle or paternal uncle?

Question:
Is it permissible for a man to shake hands with the wife of his paternal uncle or maternal uncle?

Answer:
No, the wife of his paternal uncle and the wife of his maternal uncle are not mahram (a relative one may not marry) to him. He is not permitted to shake hands with them or be in seclusion with either of them, because they are not mahram to him. The wife of his paternal uncle, the wife of his maternal uncle, and the wife of his brother are all not mahram to him. Therefore, he does not shake hands with his brother’s wife, his paternal uncle’s wife, or his maternal uncle’s wife. However, he may shake hands with his father’s wife, his grandfather’s wife, his son’s wife, and his daughter’s son’s wife; there is nothing wrong with that. As for his brother’s wife, his maternal uncle’s wife, and his paternal uncle’s wife, they are all non-mahram to him. Yes.