As the British royal family rallies around Princess Kate Middleton following her cancer diagnosis, Prince Harry may be feeling more isolated than ever, according to royal historian and expert Dr. Tessa Dunlop.

The revelations about Kate's health have shifted the spotlight away from Harry and his wife, Meghan Markle, and their ongoing controversies, leaving the Duke of Sussex in a "painful place," Dunlop suggests, as reported by US Weekly.

Speaking to The Mirror, Dunlop pointed out that Harry and Meghan have positioned themselves as an alternative to the monarchy, encouraging the public to view them as an American version of "royalty-lite." However, in the wake of Kate's health revelations, the Sussexes may find it challenging to maintain their public image without appearing opportunistic.

"Harry and Meghan posited themselves as the alternative to royalty, the couple who believed in service outside monarchy," Dunlop said. "All their branding nudges us towards sideways glances between the House of Montecito and the House of Windsor."

The royal expert also noted that Harry, who famously referred to himself as the "spare" in his memoir, may feel more marginalized than ever as the royal family comes together to support Kate. "Meanwhile, Harry is the self-identifying royal 'Spare,'" Dunlop continued. "And in the wake of his sister-in-law's health revelations, I expect he feels more spare than ever."

Dunlop's comments come amid reports that Kate and King Charles have grown closer following her cancer announcement, with the Princess of Wales even helping to mend the rift between the king and his eldest son, Prince William. Harry, who is believed to have learned about Kate's diagnosis along with the rest of the world, may feel left out of these important conversations and developments within the royal family.

The timing of Meghan Markle's upcoming lifestyle brand, American Riviera Orchard, which Dunlop suggests leans into California glamour, could also contribute to the growing divide between the Sussexes and the rest of the royal family. As Harry and Meghan prepare to visit the U.K. this summer, Dunlop warns that they must navigate their time abroad with "extreme care," as the "timing and optics matter like never before."

While acknowledging that Harry and Meghan have faced their own challenges, including a high-speed chase in New York and constant press intrusion, Dunlop emphasizes that Kate's cancer diagnosis has rightfully shifted the public's attention and sympathy toward the Princess of Wales. "Sure, Harry and Meghan had a right to complain about press intrusion and difficult dynamics within the institution of royalty," Dunlop said. "But can anything compare with the nightmare assault on Kate over the last two months?"

The royal historian praised Kate's "spellbinding" response to her diagnosis, describing it as a "lesson in magnanimity." By thanking the public for their messages of support and reaching out to fellow cancer sufferers, Kate has set a high standard that may be difficult for Harry and Meghan to follow.

As the British royal family continues to support Kate during her cancer battle, the spotlight on the Sussexes and their controversies has diminished. Prince Harry, who has been open about his strained relationship with his family, may find himself feeling more isolated and "spare" than ever as he watches his loved ones come together in the face of adversity.

The coming months will be crucial for Harry and Meghan as they navigate their public image and relationship with the royal family. As Dunlop warns, the couple must tread carefully to avoid appearing opportunistic or insensitive in the wake of Kate's health struggles, while also finding a way to maintain their own identity and purpose outside the monarchy.