Prince William, Kate Middleton and Prince Louis
Prince William and Kate Middleton are expected to break a royal protocol for Prince Louis. Pictured: Prince William and Middleton depart the Lindo Wing with their new born son Prince Louis of Cambridge at St Mary's Hospital on April 23, 2018 in London. Getty Images/Chris Jackson

Prince William and Kate Middleton may continue to break a certain protocol for Prince Louis.

In April, the Duke and Duchess of Cambridge welcomed their third bundle of joy. According to Kara Godfrey, a journalist for Express, Prince William and Middleton are likely to ignore a travel protocol that they have already violated in the past.

The royals have a certain practice that forbids two royal heirs to travel on the same plane. This is to ensure that the line of succession won't be affected in case of a crash. So, Prince William and Prince George should not travel together. This applies to Prince Louis traveling with his parents.

However, Prince William and Middleton have already broken the said rule when they traveled to Canada and enjoyed a tour in Australia and New Zealand with their firstborn. Godfrey believes that this scenario will happen when Prince Louis gets older. He will likely join his parents on a trip abroad just like his older siblings.

Whenever the Duke and Duchess of Cambridge travel abroad with their children, they have to ask the Queen's permission. For Prince George's case, the monarch reportedly granted their request. The said travel rule was not official and "it is something that the Queen has the final say on."

In fact, they may have broken this rule already. It was reported earlier that Prince William and Middleton flew to Mustique with their three children, 5-year-old Prince George, 3-year-old Princess Charlotte and 3-month-old Prince Louis. The family of five was joined by the Duchess of Cambridge's parents, Michael and Carole Middleton.

Prince William and Middleton were even photographed enjoying a wild night out as they danced with the locals on the island. According to an eyewitness, the Duke and Duchess of Cambridge "were there for the cocktails segment and kept it rather classy."

Prince William and Middleton are bound to Canada in September. The couple will reportedly visit Yukon. The duchess will accompany her husband this time after she failed to join him during his visit to Jordan.

According to the father of three, Middleton was "very upset" that she was not able to join the duke at that engagement.

"My wife Catherine is very sorry she cannot be here with me so soon after the birth of our son Louis, but her family remembers very fondly the almost three years she spent here as a child when her father worked for British Airways in Amman," Prince William explained Middleton's absence.