The woman over there is Julia and Mary’s mothermary后面加了个S

The woman over there is Julia and Mary’s mothermary后面加了个S
The woman over there is Julia and Mary’s mother
mary后面加了个S

The woman over there is Julia and Mary’s mothermary后面加了个S
那边的女人是julia和mary（他们两个）的妈妈
s代表所有格.
如果是The woman over there is Julia‘s and Mary’s mother
的话,这个mother应该改为mothers,作为两个人各自的妈妈（两个妈妈）