Their first names were Mary but that was never used on its own. Instead they formed their names by joining Mary with their second name.

I have some friends, Norm and Mary Jane, who had five daughters and no sons. They named them all Mary ______. With different middle names. Some are known by both together, some by their middle names only. It's Norm that I have the most fun with. One day, I decided he should suffer the same fate as the six ladies in his life. From that day forward, he has been known as Mary Norman!