Reply #4: In Iran, it's known as siqeh. It's a concubinage, a form of marriage

[Skidmore]

contracted for anywhere from 1 hr to a lifetime. A very old practice, it came to be frowned upon during the Shah's reign, but the practice returned after Khomeini came into power. I believe it is something found in Shi'a cultures. A siqeh wife does not have all the rights of the primary legal wife. She is afforded some protection during the course of the contract. However, she and any children born of during the siqeh marriage have no rights of inheritance.