The royal brothers currently occupy a joint household at the London palace with their wives Catherine, Duchess of Cambridge, and Meghan, Duchess of Sussex, as well as William and Catherine's three children, Prince George, five, Princess Charlotte, three, and newborn Prince Louis, six months.
But with Harry and Meghan expecting a baby of their own in Spring next year, it has been reported that plans are being put in place for a formal division of the royal household, and the creation of separate courts to reflect the couples' increasingly different responsibilities.
A source said: "The brothers have leant on each other and looked after each other since their mother died. But now they have their own families, they no longer rely on each other as before.
"They have become different people with different outlooks on life. Splitting the household is the obvious thing to do."
Prince William, 36, is second in line to the throne and will become the Prince of Wales when his father Prince Charles becomes King, and this responsibility will see him take on far more work than his younger brother Harry, 34, who will be able to "forge his own path".
The source added: "There is a gulf in the style and approach to the type of work that William and Kate will increasingly do as future head of state and consort, and Harry and Meghan, who have more of a blank canvas with their roles.
"When William becomes the Prince of Wales, he will take on a lot of extra responsibility, including the Duchy of Cornwall and all that entails. Harry and Meghan have none of that, and seem ambitious about forging their own paths."
And even though the brothers may remain neighbours, the management of the Kensington Palace household is thought to be likely to split too, as each family require something different.
Speaking to the Sunday Times newspaper, the source said: "If you have one private office trying to manage both, things get difficult. William and Harry's double act has naturally been supplanted by the two couples and their families."