Stepmom

So my SO is now telling me that the children can't call me Mama because his ex wife doesn't want me to be Mama and her bf can't be papa even though he's been papa this entire time, I gave up Mama and told them to call me by my first name.

I'm going to marry him.

I'm hurt because I was looking forward to my sweethearts to call me Mama once more.

So I need help, what should the kids call me, I don't want my name it feels disrespectful.

The children are 8, 7, and 5, and they choose to call me Mama. It hurt to have them call me by my name but I don't want them to continue to call me that after my fiancé and I are married.

*UPDATE*

So great news she agreed I can be mama, thank you to everyone that was nice and gave me actual advice.

It wasn't fair that her boyfriend could be papa and I had to go by my name. My wonderful fiancé stood up to her and said he either goes by his name or we can have them as papa and mama.

THANK GOD I DONT HAVE TO CORRECT THE KIDS ANYMORE IM MAMA!!