While the card was a standout feature of the post, some eagle-eyed fans speculated Kate may favour her daughter, after she chose to lead the tribute post with a snap of Charlotte.
In the never-seen-before snap of Charlotte, four, the youngster is being carried by her mother Kate, while George, six, is seen in the background with their father William.
While the Duchess has never spoken about having favourites, it’s not the first time she has seemingly chosen her daughter over George.
Earlier in the year, Kate shared another cute photo of Charlotte after speaking on Giovanna Fletcher’s parenting podcast.
Speaking on the Happy Mum, Happy Baby podcast, the Duchess said the time between giving birth and sending your children to school can be especially daunting for new parents.
“Having had such a wonderful support network through pregnancy and delivery from nurses and midwives, it’s then a very lonely period between then and perhaps going into the educational system,” Kate admitted.
Kate, who appeared on the podcast to talk about her five big questions survey, said while there are plenty of prenatal support services, there needs to be more postnatal intervention.
WATCH: Kate Middleton gets emotional over photo of Charlotte