'Teen Spirit' in Tiaras: An Inside Look at Prince William and Kate Middleton's Rule-Breaking Romance in the House of Windsor

Prince William and Catherine, Princess of Wales, both 42, are "still very into each other" like "teenagers in love" after a relationship spanning nearly 23 years.

Royal expert Roya Nikkah told Fox News, "One’s always looking out for the other. Recently, when they were in Southport together, you could see that… she was a bit more vulnerable. I think they’ve got each other’s backs."

"I think when you have that weight of public scrutiny on you, it’s very hard to keep a little bit of your private life private because you are so publicly scrutinized," she added. "But if you look at the video they put out when [Kate] announced she’d finished chemotherapy, we never get to see them like that."

Nikkah continued, "A lot of people were quite surprised to see how open they were in terms of letting the cameras film them as they were, as they would like us to see them, which was hugging a lot, kissing, and being extremely close physically on a blanket."

The future king and queen have been a couple since early 2002, but long before they met at the University of St Andrew's in 2001, fate seemed to be destined for the pair.

"Princess Kate is thought to have attended the same gap year program in South America just weeks before Prince William," a publication revealed.

Their Royal Highnesses first met at the Scottish college during the fall of 2001, and according to singer-songwriter Laura Warshauer, there was a connection between the two from day one.

"Whenever Kate was in the room, Will was obviously paying attention to her," the singer told an outlet. "When we'd be sitting at lunch in the dining hall and the two of them would be talking, it was amazing to see how natural it was, how they had so much to say to each other. Looking back, there were all these small moments — certainly moments where I was like, 'Wow, this could really be something.'"

The millennial generation, modern future king and queen got to know one another "for months" before finally starting dating in the first quarter of 2002. The Princess of Wales revealed in her and William's 2010 engagement interview that she was "shy" when she first met the "strikingly good-looking" prince destined to wear St Edward's Crown.

"It did take a bit of time for us to get to know each other but we did become very close friends from quite early," her future Royal Highness spilled.

The princess beat cancer in early September when she finished a six-month round of preventative chemotherapy.

"I think, hopefully, Catherine will be doing a bit more next year," the heir to the British throne told the press on Saturday, November 9. "So, we’ll have some more trips maybe lined up."