Look Back at Prince William and Prince Harry in Their Teens

Prince William was grinning widely on his first day at Eton at age 13. 

When he was 14, Prince William joined his family on a ski trip at Klosters-Serneus, an alpine ski resort in Switzerland. 

Alongside their father, Prince Charles, William and Harry posed for photographers during a summer trip to Balmoral, Scotland.

William, 15, looked sharp in a classic tux at the premiere of Spice World in London.

Harry rocked a red bandana around his forehead as he skied during a family holiday in Switzerland. 

William hit the slopes with his dad during a ski holiday in Whistler, Canada.

Harry wore a traditional coat tail as he left his house for his first day of lessons at Eton College.

Harry, 14, flashed a smile as he headed into the Apollo Theatre in London to see a production of Doctor Doolittle.

With one arm in a sling following surgery, William gave a wave with his other hand at the christening of his godson, Prince Constantine Alexios of Greece, at the Greek Cathedral of Saint Sophia in London.

The royal brothers attended the wedding of Sophie Rhys-Jones and Prince Edward at St. George's Chapel in Windsor. 

The brothers chatted during a visit to Highgrove, Gloucestershire, in England.

The now-Duke of Cambridge suited up for the Queen Mother's 99th birthday party.

Prince Harry, 15, flashed his braces and his smile on Christmas Day.

Princes Harry, Charles and William all showed off their big smiles at the youngest royal's Confirmation at Eton.

The sun even gets in the eyes of royals! Prince Charles and his sons were a bit blinded by the bright snow while on holiday in Switzerland.

To commemorate his 18th birthday, Prince William rocked a black jacket over a Union Jack vest with the words "groovy baby" written at the front. 

Prince William, 18, and Prince Harry, 15, accompanied their father to the Queen Mother's 100th birthday at Buckingham Palace. 

Prince William flashed a huge grin as he was photographed in Tortel, Chile, during his gap year.

Just palling around! Harry, 16, goofed around with two friends at the Beaufort Polo Club in Gloucestershire, England.

Prince William, 19, and Prince Harry, 17, sweat from the sidelines of a polo match in Gloucestershire, England.

The brothers stood behind their father at a celebration for the Queen Mother's 101st birthday in London.

A 19-year-old Prince William looked like a catalog model on his first day of school at St. Andrews University in Scotland.

Harry, 17, donned a striped jersey as he played in the traditional Eton wall game at his school in Berkshire. 

Harry, 17, and William, 19, bonded with their dad during a trip back to Klosters, Switzerland. 

The redheaded prince looked quite happy after his team beat his father's squad in a polo match at the Beaufort Polo Club.

Safety first! The royal brothers took part in a charity polo match in Tidworth, United Kingdom.

One day before his 18th birthday, Harry took a penalty kick while visiting a youth soccer squad at West Ham United's Upton Park Football Ground in East London.

Prince Harry, 18, blushed as he received gifts of flowers and candy while meeting royal fans after Christmas Day services in Sandringham. 

Prince Harry, 18, relaxed in his room at Eton College.

The 18-year-old redheaded prince wore his school dress -- a black tailcoat, waistcoat, pin-striped trousers and "stick-ups," which consisted of wing collars and a bow tie to mark that he was House Captain of Games -- one month ahead of finishing his studies at Eton.

Now known as the Duke of Sussex, a then 19-year-old Prince Harry threw up a victorious fist pump as he left school.

Harry, 19, worked as a Jackaroo on a cattle property in Australia owned by friends of his late mother, Princess Diana, during his gap year. 

Sporting one of the shortest haircuts of his teens, a 19-year-old Harry posed for photographers at the Mant'Ase Children's Home in Lesotho.