Polygamy

Polygamy is a term for when someone has a marriage with multiple people. It can be an umbrella term for polyandry and polygyny, or it can be a marriage with involving several people of different genders. Polygamy is illegal in many Western countries.

History
Unlike what modern society tries to deny, polygamy has been around since the ancient times in almost every culture or religion nameable. It is shown in many cases throughout history, deciptions are shown within art and old photography, as well as religious books, such as within the Bible.

Polygamy vs Polyamory
Polyamory is when one desires a relationship with two or more people while polygamy is when one marries multiple partners at the same time.

Resources

 * https://en.wikipedia.org/wiki/Polygamy#Canada
 * https://www.psychologytoday.com/us/blog/the-polyamorists-next-door/201807/what-is-the-difference-between-polyamory-and-polygamy