Prince William and Kate Middleton have epitomized stability ever since they married in 2011, which is why it’s hard to imagine that prior to their marriage, they had a bit of a tumultuous on-again off-again relationship with one another. Now, a royal biographer is speaking out to discuss the “secret pact” they made with each other after one of their breakups.

In her book “Kate: The Future Queen,” the royal expert Katie Nicholl talked about some of William and Kate’s breakups. She alleged that in 2007, William felt so much pressure to propose to Kate that he actually broke up with her in a telephone call. Nicholl added that this breakup only lasted a few months, however, and that William and Kate went on to make a “marriage pact” while they were on vacation together.

“There on the paradise island, William promised Kate that he was in the relationship for the long term,” she said, according to The Sun. “For the very first time, they talked seriously about marriage, and with the ocean before them and beneath the night sky, they made a pact to marry.”

As part of this pact, William agreed that he would only propose once he had finished his army training. Kate opened up about this breakup in a 2010 interview, saying it was difficult for her not to become “consumed” by the relationship.

“At the time, I wasn’t very happy about it but actually it made me a stronger person,” Kate explained. “You find out things about yourself that maybe you hadn’t realized, or I think you can get quite consumed by a relationship when you are younger. I really valued that time for me as well although I didn’t think it at the time. Looking back on it.”

William and Kate went on to marry in 2011, and it appears it has been smooth sailing for them ever since. They have gone on to have three children: Prince George, 7, Princess Charlotte, 5, and Prince Louis, 2.

Hello Magazine reported that Monday marked the tenth anniversary of when William and Kate announced their engagement, and one of their wishes from this interview has since come true.

When asked if they wanted to have children in the future as they announced their engagement, William replied, “I think we’ll take it one step at a time. We’ll sort of get over the marriage first and then maybe look at the kids. But obviously we want a family, so we’ll have to start thinking about that.”

“And I hope we will be able to have a happy family ourselves,” Kate added.

Given how happy William and Kate are with their three kids, it’s safe to say this wish came true in a big way!