How Kate Middleton's Father's Day Tribute to Prince William Broke Royal Tradition

Kate Middleton broke the royal norm when sharing her loving Father's Day tribute to Prince William over the weekend.

On Sunday, June 16, the Princess of Wales took to Instagram with a new family photo that featured the doting dad, 41, with the royal couple's three children–Prince George, Princess Charlotte and Prince Louis. While the adorable new portrait is very much in line with what the royal, 42, has made a habit of posting, there was one easy-to-overlook detail that swayed from royal tradition.

Instead of signing off with the usual "W & C," the royal couple's initials, the princess signed the post in a way that included the children. "We love you, Papa. Happy Father’s Day ??," the caption read. Signed, "G, C & L."

Though Kate is still undergoing treatment for an unspecified type of cancer she was diagnosed with earlier this year, it appears as though she's eager to return to a sense of normalcy.

In the six months or so since she went public with her diagnosis, Kate has refrained from entertaining the spotlight and attending royal engagements as she remains focused on her health, healing and spending time with her family through the hardship.

Kate has also kept off social media for the most part, unless it was to pay tribute and share her condolences or celebrate her loved ones by marking birthdays and holidays like this one with a meaningful photo.

On Saturday, June 15, one day before she shared her sweet Father's Day tribute to William, Kate made a rather unexpected appearance–ringing in her first public engagement since Christmas–at the King's Birthday Parade or Trooping the Colour. After she apologized for missing the rehearsal, the princess pleasantly surprised onlookers as she rode in the carriage with her kids and posed with the family on the balcony.

Next: Kensington Palace Offers Rare Comment on Kate Middleton's Cancer Treatment