Family photos of Princess Charlotte and Prince George, taken by their mother the Duchess of Cambridge, are to be released by Kensington Palace this evening (6 June).
Kensington Palace announced the news on Twitter this morning.
The tweet said: "We'll be posting a very special photo of Prince George & his little sister Princess Charlotte late tonight. Can't wait to share it with you!"
The pictures, which were taken last month by their mother Kate, who is a keen amateur photographer, are expected to show the pair in an informal setting.
Kate's father, Michael Middleton, took the first official picture of George, which was released when he was less than a month old, in August 2013.
The informal images taken in the garden of the Middleton's family home in Buckleberry showed the prince with the Duke and Duchess, their black cocker spaniel Lupo and the Middleton family's golden retriever Tilly.
Kensington Palace also posted a picture of the thousands of letters send by well-wishers following the royal birth on 2 May.
It said: "The Duke & Duchess are very grateful for the wonderful messages they've received on the birth of Princess Charlotte."
The news came a day after it was announced that Princess Charlotte would be christened by Archbishop of Canterbury, Justin Welby, on 5 July.
The service will take place at St Mary Magdalene Church at the Queen's Sandringham Estate in Norfolk, where Prince William and Kate Middleton live.
Princess Charlotte is fourth-in-line to the British throne after her grandfather, Prince Charles, her father Prince William and brother Prince George, who is almost two years old.
Charlotte's brother was christened by Welby at the Chapel Royal at St James's Palace in October 2013.