Mom. ---- Unless your father in law has other children and it's one of their mothers in law. I certainly don't call my brother in law's mother in law, Mom. ---- If your father-in-law has other chlidren, who have mothers-in-law that are not your mom, then you don't have a standard name for them, do you? Most of the time, you never even meet them. But if you do know them, you refer to them as Mrs. ____, or Miss ____, or Ms. ____, or if you weren't raised to respect your elders, you might refer to them by their first names. But, the point is, there is no single answer to this question if the person is not your own mother. Therefore, this question only makes sense if the father-in-law's child is your spouse, and therefore, the first answer is the only possible answer to this question. Granted, it is not always the answer to the question. But it is always an answer, and is therefore always correct. No other answer is always correct. And before you start getting technical on another facet of this answer, yes, I know that some people don't call their mothers "Mom". So you can add "Mother", "Ma", "Momma", "Old Lady", "Mum", and any other English phrase meaning "mother". I'll exclude any non-English names for "mother" because the question was asked in English, so we can assume only English words are appropriate answers. But if it makes you feel better, add them in too.
Your mother-in-law. Or, call her by her name.
You still call her your mother in law or if you were divorced you would call her your Ex- mother in law.
You can call her by her first name or if your comfortable some son-in-laws call them mom.
Your mother's brother-in-law is your uncle.
Your mother's brother-in-law is your uncle.
Mother in-law
The mother of your wife is your mother-in-law.
Your own mother
Well if its Wife or Hansband grandma then its you grandmother in law.
Your mother-in-law.
I would just call her my second mother
I would think you would call her by her name, same as if she were your son's American mother-in-law.