It's never stated in the movie. For what it's worth, the child actors were about seven and eight during filming.
If by Mary you mean the virgin Mary then she has only one child which is jesus christ
She was 38 when she thought she was pregnant, but it was in fact some form of stomach cancer. She never had any children of her own to become her heirs.
Erica (the brunette) is 37 years old & Tina (the redhead) is 35 years old.
Mary Mary is an American Gospel duo. The members are Erika And Tina Atkins.