Portraits spanning four generations of the royal family will go on display to mark the Prince of Wales' birthday.
Sketches of the Queen Mother, the Duke of Edinburgh, and Charles' sons the Duke of Cambridge and Duke of Sussex will be displayed at Buckingham Palace over the summer.
The family portraits, from Charles' personal art collection, will be part of more than 100 works of art displayed in the Prince & Patron exhibition.
The Prince, who turns 70 this year, has also selected artworks from the Royal Collection and by artists supported by three charities Charles works with.
The portraits include a never-before-seen pencil sketch of Prince Philip by Bryan Organ. The final portrait, completed in 1983, hangs in the National Portrait Gallery.
Two preparatory oil sketches of William and Harry in their "blues and royals" household cavalry regimental uniform by Nicky Philipps are also going on public display for the first time.
They usually hang in Highgrove - the private residence of Charles and the Duchess of Cornwall - while the double portrait commissioned in 2009 is displayed in the National Portrait Gallery.
A sketch of the Queen Mother wearing Queen Victoria's diamond jubilee brooch is also to be shown.
A sketch of the Queen Mother wearing Queen Victoria's diamond jubilee brooch is also to be shown (Nicky Philipps/RCT/PA) [/caption]
It was produced by Michael Noakes, who died this year, as a study for a painting marking the silver wedding anniversary of the Queen and Philip in 1972.
In a message recorded for visitors at the palace, Charles says: "I acquired it from the artist as I felt it brilliantly captured her likeness and, above all, reminds me of the essence of her personality.
"I admire it often when in residence at Clarence House."
The exhibition can be viewed as part of a visit to the summer opening of the state rooms at the palace from July 21 to September 30.