I would consider Moses as a polygamist. For further info, this chart might be helpful in locating other polygamists in the Bible:
http://www.biblicalpolygamy.com/polygamists/
As for Mary, I've heard, tradition say that Joseph was a widower, with children and then married Mary. I doubt Mary was a perpetual virgin. However, the Bible doesn't tell us that Joseph was married before Mary, either way.
Older siblings of JESUS, though, would prove Joseph as a widower.
-Bro. Alex