The Boleyn Sisters
16th century seductresses Anne and Mary Boleyn had their fair share of royal rendezvous. Anne married King Henry VIII and was the Queen of England from 1533 to 1536 until she famously lost her head. Her older sister, Mary, had actually been one of the king's mistresses, and it is widely believed that Mary also went on to have an affair with the king of France, who happened to be Henry's rival. That's one way to get revenge.
[Yes, that's Natalie Portman and Scarlett Johansson from that time they played them in The Other Boleyn Girl]