TORONTO -- As the Duke and Duchess of Sussex step back from the Royal Family鈥檚 frontline duties, could a new pair step forward?

At least one royal expert believes sister princesses Beatrice and Eugenie could fill Harry and Meghan鈥檚 vacancy.

Robert Lacey, a royal biographer and historical consultant on Netflix drama The Crown, told HELLO! magazine that it鈥檚 actually 鈥溾 the pair will step up.

鈥淚f two go out, two have got to come in, and those two have got to be Beatrice and Eugenie,鈥 he said.

CTV鈥檚 royal commentator Richard Berthelsen isn鈥檛 as convinced, calling it an 鈥渙pen question.鈥 The sisters have 鈥渘ever been particularly popular,鈥 he said in an interview with CTVNews.ca. Not to mention, their father, Prince Andrew, recently stepped back from royal duties following scandal surrounding his former association with the now dead convicted sex offender Jeffrey Epstein.

鈥淚t鈥檚 possible that (Beatrice and Eugenie) may do more within the realm of what they have opted to do, which is some light charity work,鈥 Berthelsen said Monday.

It鈥檚 another question whether the sisters could travel around the Commonwealth and undertake official royal duties for the Queen. That is 鈥渁 little hard to imagine,鈥 he continued.

But the pair stepping up could be the beginning of a solution to what Berthelsen called a 鈥渓abour shortage鈥 in an aging Royal Family. Some members, including some of the Queen鈥檚 cousins who still perform duties, may soon age out of their positions. Princesses Beatrice, 31, and Eugenie, 29, also would address another issue, said Berthelsen:

鈥淭here鈥檚 kind of a shortage of princesses,鈥 he said. 鈥淢ost of the members of the Royal Family that are prominent are males. There鈥檚 a bit of a gender imbalance.鈥

Earlier this month, the Queen met with Charles, William and Harry in Sandringham. While the Duke and Duchess of Sussex were acknowledged as the subject of the meeting, Berthelsen said at the time that the scope was probably much wider. The so-called 鈥淪andringham Summit鈥 likely had implications for other junior members of the family, including Beatrice and Eugenie. The talks may have helped define the sisters鈥 positions further as Harry and Meghan sought a life away from the Crown.

The sisters, who are the daughters of Prince Andrew, have been considered by some experts as a model for how Harry and Meghan could move forward as more junior members of the Royal Family. In fact, Harry has even mentioned his cousins鈥 lifestyle as a 鈥渕odel,鈥 Lacey pointed out. Beatrice and Eugenie live relatively private lives and are financially independent, but maintain a balance between occasional royal duties and charity work with a few royal patronages.

鈥淭hey鈥檙e not really seen as representing the Queen -- they represent themselves,鈥 said Berthelsen. 鈥淭hey鈥檙e kind of in the same world that Prince Harry and the Duchess of Sussex are now.鈥