This happened to Samuel's great great great grandfather in England.
His wife became sick after the birth of her only child, so her sister moved in to help with looking after the family. The wife died and he wanted to marry the sister. According to the church he wasn't allowed to because she was family and you can't marry family. So not only did the church ban polygamy, but women that you weren't even blood related to as well. They ended up going to France and eloping instead.
They had 16 children, one of which was Samuel Dennis who moved to New Zealand and married a Sarah. These are Samuel's great great grandparents. We got married in the church where they are buried, so one of our wedding photos was standing beside their grave stone.