See Prince George's Best Big Brother Moments with Charlotte and Louis!

Prince George was all smiles in the official portraits for the christening of his baby brother, Prince Louis, taken on July 9, 2018.

Prince George lets Princess Charlotte and Prince Louis take center stage in their first official portrait as a family of five.

Prince George, Princess Charlotte and mom Kate Middleton played on the sidelines of dad Prince William's, charity polo match in June. George looked on as Charlotte showed off her tumbling skills.

Prince George leads the chase in the grass.

In a typical big brother move, Prince George runs ahead and lets Charlotte chase after him.

Prince George smiles subtly when walking up to the Lindo Wing of St. Mary's hospital to meet his little brother, Prince Louis, for the first time in April 2018.

At the end of the royal family's European tour in June 2017, George stands by Charlotte during her memorable tarmac tantrum!

At George and Charlotte's second Trooping the Colour together, he leads by example during the traditional wave from the Buckingham Palace balcony.

George, a page boy, helps Charlotte, a bridesmaid, with her flower wreath at the May 2017 wedding of their aunt, Pippa Middleton.

George entertains a 16-month-old Charlotte with a bubble machine during a children's party on their Canada tour in September 2016.

An almost 2-year-old George peeks into the pram at Princess Charlotte's christening in July 2015.

Prince George gives Charlotte a kiss on the forhead (a pose she later recreated with baby Louis!) in her first official portrait in May 2015.