It's the kind of mistake that happens all the time. Besides seeing photos of her step-grandson, Camilla was also gifted a big teddy bear to pass along to the royal baby.
Markle wore a white sleeveless dress, while Prince Harry sported a grey suit.
Asked what parenting is like, the Duke of Sussex said: "It's great".
Its shawls have also been used previously by other members of the Royal Family.
Master Archie Harrison Mountbatten-Windsor is the first child for Meghan Markle and Prince Harry and early reports indicate there is no special meaning behind the name Archie. Meghan appeared to be in excellent health when she and Prince Harry appeared in Windsor Castle with baby Archie and answered press questions.
She said the baby had "the sweetest temperament" and has "just been a dream".
Meghan Markle and Prince Harry have finally shared their son's name with the world!
"I'm so incredibly proud of my wife and as every father and parent would ever say, your baby is absolutely awesome, but this little thing is absolutely to die for, so I'm just over the moon", he told reporters.
Prince Harry added that Baby Sussex's looks have been "changing everyday".
The photo shows little AHMW swaddled in the arms of his mother, while surrounded by his maternal grandma Doria Ragland and paternal great-grandparents Queen Elizabeth II and Prince Philip.