In the first sketch, a beaming Queen Elizabeth II is drawn with blonde hair. She wears a yellow and red gown, purple gloves and tiara, red earrings, and a handbag.
The other depicts “Papa” Prince Philip in a tuxedo and bow tie.
A young Charles created the works between 1953 and 1955, when he was about five or six years old.
Both drawings are slated to sell for £5,000 to £10,000 (US$6,330 to US$12,660) at Hansons Auctioneers on Friday.
The auction will also incorporate cards drawn by a very young Princess Anne, addressed to her father.
The monarch’s passion for art has followed him into his older years. Just months back, a watercolor painting he had done was auctioned off for US$6,500.
Besides the two portraits of his parents, the sale will include eight of the young royal’s other masterpieces, including a picture of birds and a painting of a rabbit. One drawing imagines a delivery van with the words, “Happybright, Mr Charles’s Shop.”
“Given a crayon and pencil, nearly every child’s first drawings depict their family. Our King was no different,” explains the auction house’s owner, Charles Hanson, in a statement. “This collection will help people relate to him even more in his role as our monarch.”