Prince Louis is growing so fast! Prince William just revealed his new milestone

On the same day that his wife Duchess Kate celebrated her birthday, Prince William was seen at London's Air Ambulance Charity. The prince shared some information about his children.

As he received gifts for his wife, William revealed that one of the presents would come handy for his last born son, Prince Louis.

While visiting London’s Air Ambulance Charity without his wife of seven years, Duchess Kate, 37, Prince William, 36, received several cards and presents on her behalf. One of the gifts was a red squeezy helicopter toy.

For more on this story go to our Twitter account @amomama_usa. Holding it in his hand, the father of three joked, "Amazing, that will go down extremely well."

He then shared a special milestone about his last born son, Prince Louis by saying, "Louis will be chewing that before long!" William indirectly revealed that his son was already teething.

The prince then opened a brightly-colored handmade card which was meant for Kate. Speaking about his children once again, he stated: "Charlotte's going to love this!"

William then continued joking by saying, "Well done you for remembering, that's very impressive." He added: "I did remember this morning, so I was ok."

A staff member tried to find out what the family had planned for Kate’s birthday by asking, "Are you doing anything special today?" Sharing no information, the prince simply replied "That would be telling!" before everyone burst into laughter.

The family of five, including Prince George, celebrated Kate’s birthday privately after George and Charlotte returned from school on Wednesday. William was at London's Air Ambulance Charity for their 30th-anniversary campaign.

Earlier in the day, he was named patron of the campaign. The charity aims to raise awareness about their work and to gain support for the development of new facilities.

Last month, the Duchess joked that little Louis was already working on his Royal wave at 7-months. She shared the joke while chatting with well-wishers outside the RAF Akrotiri in Cyprus during her and her husband’s special Christmas visit.