The mother of your wife is your mother-in-law.
Unless you are in a polygamous marriage, you are your husband's wife, so you would call her your mother.
Your mother-in-law.
I would just call her my second mother
mother/father in law
Cousin - In - Law
Well if its Wife or Hansband grandma then its you grandmother in law.
If you don't want to call your step-mother 'mom' or 'mother' then ask her permission to call her by her first name.
You would call your wife's sister your sister-in-law. If your wife would have a brother he would be your brother-in-law. It is the same thing for a husband's siblings. Your wife's mother would be your mother-in-law. Her father would be father-in-law.
He would call her his 'skoonma' which means mother-in-law and you would call her: my seun se skoonma which means my son's mother-in-law
Your mother is not related to your wife's mother.
Your mother is not related to your wife's mother.
If you are close to your step-father or he has formally adopted you, you can call his wife you mother or step-mother, however, she is actually not related to you at all. Either your mother has died or your step-father must have divorced her to marry someone else. That means you actually have no connection to him anymore.