There are reportedly “three key points” that will guarantee a lasting marriage between Prince William and Kate Middleton.

Express UK reported that Princess Diana’s astrologer previously made the assertions in a documentary. This came after the two personalities tied the knot in 2011 after almost a decade of dating.

As recalled, Penny Thornton said that the Duke of Cambridge found a “maternal bond” in his wife. He, then, added the marriage will be “long, happy,” and “faithful,” provided that the royal-born Prince feels “cosseted,” “adored,” and “has that kind of wonderful connectedness” with the Duchess of Cambridge.

The late Princess of Wales’ biographer reportedly consequently asserted that Kate Middleton has been “very loyal” to her husband. Richard Morton, also, pointed out that the future Queen Consort has been “very supportive,” adding that Prince William has always “yearned towards the stable,” as well as the “steady.”

The Duke and Duchess of Cambridge are now approaching their 11th wedding anniversary. It is unclear how the royal couple will celebrate the day but, reports noted that the “love is still very much alive” between them.

Ahead of the relationship milestone, Hello! magazine released a report about the pair’s “secrets” to their marriage. On top of it all, it claims that Kate Middleton and Prince William always “have fun.”

It, then, references the royal-born Prince’s previous statements, sharing that they “both have a very fun time together” and a “very good sense of humor about things.”

The outlet continued that the future King and Queen Consort's other secrets to long-lasting marriage include supporting each other, building an equal partnership, maintaining independence while in the relationship, creating close bonds with their respective in-laws, and having date nights.

Earlier in February, Good To Know released a similar report, as well, about the royal couple, making their marriage work. But, the post appears to have centered on Kate Middleton, specifically her “personal sacrifice.”

As stated, the claims were made by royal experts who spoke to Channel 5’s documentary titled, “William & Kate: Too Good To Be True.”

Tom Quinn recalled how the Duchess of Cambridge “tweaked her personal style” to look and become “more appropriate” for a member of the Royal Firm. He said that the royal’s clothing began to “reflect what people saw in her character, which is “kind of restraint” and “kind of modesty.”

The expert, then, emphasized that it did come about because the now-parents of three were about to announce their engagement. He, also, noted that it was the time when Kate [Middleton] was “starting to behave in ways which would be seen more appropriate for a future Queen.”