Kate Middleton and Prince William's photo of Prince George sitting with them in a window is reminiscent of past portraits taken of Queen Elizabeth and Prince Charles Credit: JASON BELL/CAMERA PRESS/REDUX

Royal flashback! Kate Middleton and Prince William's latest family portrait isn't just a window to their lives -- it's also a window to the past. The photo, which shows the Duke and Duchess of Cambridge posing with their baby son, Prince George, and their beloved dog, Lupo, in a window at their Kensington Palace apartment, echoes past royal portraits of Queen Elizabeth II and Prince Charles taken by royal photographer Lisa Sheridan.

After receiving an official royal warrant in the 1940s, Sheridan completed three generations of royal commissions. Among the many images in her so-called Studio Lisa collection is this picture from June 1936. It depicts a young Princess Elizabeth -- then just 10 years old -- at a window in Y Bwthyn Bach, or "The Little House," a miniature cottage given to the future queen and her younger sister, Princess Margaret, on behalf of the people of Wales. (The two girls were the only children of Prince Albert, Duke of York, later King George VI, the subject of the 2010 Colin Firth film The King's Speech.)

Two other photos, both from September 1952, show the monarch-to-be 16 years later, by which time she had her own family. One, a sweet black-and-white shot, features the then-26-year-old princess with her husband, Prince Philip, Duke of Edinburgh, and their two kids, Prince Charles, then 3, and Princess Anne, then 2, peering out of a window at Balmoral Castle in Scotland.

The other picture from that set is a stunning color portrait of Princess Elizabeth at that same window, this time with just her son, Prince William's father and Prince George's grandfather. Both mother and child appear to be looking at something in the distance and smiling.

As previously reported, Kate Middleton and Prince William's family photo was taken by photographer Jason Bell, who also preserved Prince George's October christening on film last year. Taken in mid-March, it was released on Saturday, March 29, in advance of the couple's three-week tour of Australia and New Zealand.