In fact, as depicted in the first episode of the latest season, Charles only met Diana because he was dating her older sister.
Here's a rundown of everything we know about the late royal's sister and her short-lived romance.
The eldest child of John Spencer and Frances Shand Kydd, Sarah was born in 1955 and is six years older than Diana. Raised in an aristocratic family, the sisters grew up in the same circles as Prince Charles.
In 1977, Charles, 28, began dating Sarah, who was 22 at the time. Not too many details have been revealed, but it's reported that they went on a trip together to the Swiss ski resort Klosters.
It's unknown how Charles was feeling about their relationship, but things seemed to come to blows when Sarah gave a "disarmingly frank" interview where she admitted she would "not marry Charles if he were the dustman or the King of England," a reporter noted.
“Charles makes me laugh a lot. I really enjoy being with him,” she said over lunch. “But there is no chance of my marrying him. I’m not in love with him. And I wouldn’t marry anyone I didn’t love."
And while we admire her honesty, royal biographer, Andy McSmith recalls in his book, No Such Thing as Society, that it was this interview that would be her social undoing. From there she was allegedly "frozen out of the royal entourage."
But it seems that the pair weren't on bad terms as she would later introduce him to her younger sister, Diana. And when questioned about her feelings about their 1981 engagement she quipped, "I introduced them. I'm Cupid."
Sarah ended up marrying and having three children with Neil Edmund McCorquodale in 1980 and the pair are still together today.
For many years, Lady Sarah was the president of the Diana, Princess of Wales Memorial Fund—an independent charity established after Diana's tragic death in 1997 to carry on her legacy of humanitarian work.