Princess Charlotte may be just four days old, but her parents are already thinking about adding to their growing family again.
"I think Kate and William could have the perfect ending with a boy and girl," India Hicks, a cousin to Prince Charles, tells PEOPLE exclusively. "But I suspect they won't stop there."
It's a sentiment echoed by several others who are close to the royal couple.
"I would put money on them having more," a confidante tells PEOPLE.
Last month, as #GreatKateWait mania hit fever pitch and speculation about the gender was running wild, another friend predicted, "Whatever this baby is, there will be another one."
Hicks knows the royal family well. A former bridesmaid to Princess Diana, she says that the late princess "would have been deeply moved" by her granddaughter's name.
As for the proud royal grandpa, who had made no secret of his preference for a granddaughter, "I am sure he is delighted," says Hicks. "How could he not be?"
Describing the name as "very British and very reassuring," the 47-year-old former model, mom of four and author of a newly released interior design book, India Hicks: Island Style, notes that the order of the middle names is carefully considered in royal circles.
"There is always a precedence to the order to the middle names," she says. "Elizabeth quite rightly first, and Diana to follow."
When William and Kate's little prince was born in July 2013 and named him George Alexander Louis, they paid tribute to Hicks' grandfather, Louis Mountbatten, 1st Earl Mountbatten of Burma, who was a close mentor to Prince Charles.
"My mother and aunt were delighted," says Hicks, "despite it being the last name!"
For much more on Princess Charlotte's first days at home with William, Kate and big brother George, pick up this week's issue of PEOPLE, on newsstands Friday.