Unfortunately there isn't much you can do except accept it. If you try to come between them for whatever your reason maybe this will just cause problems between you two then if your mother in law gets involved it will become very unpleasant.
It is his mother and really there is nothing wrong with how close his mother and him are - lets face it she won't be around forever and then who will he run too? I realize you may feel set aside but he will always need her and he needs you as well just in a different way.
Take Care & Good Luck
Joan's mother was primarily a mother and housewife.
If you are a child of her first husband, then her second husband is your step-father. However, if your mother married her second husband after you became an adult and established your own household, you may choose not to consider him a step-father, but merely her second husband. The generally acceptable method to address your step-dad is to use his first name. Or "Dad", or any nickname HE wants you to use.
He's accused by poisoning the husband of his sister.
She would be just your sister's Mother-in-Law, but no special name exists for your relation to her.
Your father's brother is your uncle. Your mother's sister's husband is your uncle. The English language makes no distinction based on whether the brother is older or younger.
Someone too close to their mother.
Too Close for Comfort - 1980 The Sound of Mother 4-19 was released on: USA: 10 November 1984
Your mother's sister's husband is your uncle, but his mother is not related to you.
Your mother's husband's sister is your mother's sister-in-law. Her sister-in-law's husband is not related to your mother, but is her husband's brother-in-law.The most common ways of referring to him would be "my sister-in-law's husband" or "my husband's brother-in-law."
Your husband's mother's sister is your husband's aunt. She is not realted to you.
Your mother's sister is your aunt and her husband is your uncle.
Your mother's sister's husband - would be your uncle.
Mother Nature's husband is Father Nature.
In most families she would still be referred to as your mother-in-law. If you remarry, you would introduce her as your first husband's mother.
Your mother's sister is your aunt. Her husband is your uncle.
Lord Vishnu is the husband of mother earth.
The word for mother's sister's husband in Hindi is "मामा" (mama).