Prince Charles and Princess Diana wed in 1981 and had two kids — Prince William and Prince Harry. However, there are crazy rumors that suggest that the two might have had a secret daughter.

Allegedly, before Diana married into the family, Queen Elizabeth forced the future princess to test her fertility. In December 1980 (months before her marriage to Charles), the Queen had Diana undergo gynecological tests to confirm whether or not she is capable of having children, according to Daily Mail.

Rumors suggest that during the tests, Diana’s eggs were harvested and successfully fertilized with Prince Charles’ sperm. Charles and Diana’s engagement was in order by then. After the procedure, the doctors were ordered to destroy the embryo. But apparently, one of the team, a “rogue doctor” who examined the princess, ended up not destroying them. Instead, he “secretly held one of the embryos back and implanted it in his own wife,” Daily Mail wrote. Unknown to the wife, she became the surrogate mother of Charles and Diana’s child.

The baby girl, Sarah, was born in October 1981, several weeks before Charles and Diana’s wedding and eight months before the birth of Prince William. It’s been reported that as she grew up, the alleged royal daughter claims that she’s always being told she’s a “dead ringer” for Diana.

In her late twenties, Sarah’s parents died in a car accident. After their deaths, she came across a diary that revealed that her mother and father weren’t her biological parents and that she was actually born from a donated embryo and in vitro fertilization. Reportedly, Sarah attempted to find the donors but instead received a menacing message on her answering machine, warning her to stop looking if she valued her life. Sarah moved to the United States out of fear for her life and now lives under a secret identity.

Allegedly, Diana admitted the she did go for fertility testing before her engagement to Charles. “I had to be checked out before they would let me marry him,” she told a close friend.

The wild conspiracy theory stemmed from Nancy E. Ryan’s book, “The Disappearance Of Olivia.” As Diana’s fan, Ryan wrote a fictional story about Olivia Franklin, an oncologist who “admired Princess Diana and wanted to emulate her.” Olivia learns she is Diana’s secret daughter from “the result of fertility tests and procedures which somehow led to another woman being implanted with a royal embryo.”

Many people, including Ryan, believed that the story could have been true. After the book was published in 2011, the media went wild for the story, and the possibilities about Charles and Diana’s secret daughter went from being just a conspiracy to being promoted as fact.

Princess Diana, Prince Harry, Prince William and Prince Charles Prince Harry, Prince William and Prince Charles at a parade in the Mall, London, during V.J. Day commemorations, August 1994. Terry Fincher/Getty Images