So let's imagine that you have a wife, but she has a sister who unfortunately passed away. Now you may be wondering why this is important, but many, many years ago in 1907, the government of England and Wales made a rule called the Deceased Wife's Sister's Marriage Act.
This rule means that if a man's wife passes away, he can legally marry her sister if he wants to. Before this act was passed, it was actually illegal for a man to marry his deceased wife's sister! That might seem pretty strange, but people used to have different ideas about what was and wasn't allowed in marriage.
Now, it's important to know that this rule only applies to England and Wales. Other countries might have different rules about marriage, so it's always good to know what the laws are where you live.
But the Deceased Wife's Sister's Marriage Act is still important because it changed the way people could think about and legally act on their romantic relationships. Overall, it made it easier for people to make their own choices about who they wanted to spend their lives with.