2. Prince William is Not Princess Diana and Prince Charles’ First Child

Talk about family secrets! We all know royal families are defined by controversy, conspiracy and treason, but having a secret child that’s been raised in the U.S. far from the spotlight is an entirely different matter.

Reportedly, Prince Charles and Princess Diana had a female child named Sarah, and she was less than a year older than William.

Her conception was used as a test of Princess Diana’s fertility and ability to produce a royal heir with Charles. The child was conceived using in-vitro fertilization, and apparently proved that Diana and Charles could, in fact, reproduce.

The reports of Sarah’s existence resurfaced when Kate and William visited New York City back in December 2014, as Kate arranged a super-secret meeting with Sarah despite being followed by press everywhere she went.

According to various reports, William is desperate to find out if Sarah really is his sister, but after Kate’s meeting with her, his wife was so stunned by Sarah’s resemblance to the Duke of Cambridge that she believes Sarah actually is his sister.