Prince Philip has never been called king for a reason.

Prince Philip is among the senior royals. He married Queen Elizabeth II on Nov. 20, 1947. However, although the monarch is his wife, he has never been called "king." According to royal expert Marlene Koenig, this is because he doesn't share the Queen's rank.

"The wife of the king is by tradition a queen," Koenig told Hello! "The husband of a queen, in most monarchies, has to be created a title. A husband does not share a wife's rank and the same goes for the husbands of Princesses."

It is believed that Princess Eugenie's future husband, Jack Brooksbank, will not receive any royal titles for the same reason. However, experts have different opinions regarding this. According to Koenig, the monarch may not offer an earldom title to Brooksbank because usually, the husbands turn down the honor.

"Jack will not be getting any title from the Queen," Koenig said. "The precedent was set by Princess Alexandra and the Hon. Mr. Angus Ogilvy in 1963. He turned down an earldom. Princess Anne and Mark Phillips also turned down an earldom from the Queen in 1973."

However, James Brookes feels that Her Majesty might offer Princess Eugenie's groom a royal title. If this happens, it will depend on Brooksbank if he accepts or rejects it.

"Eugenie and her sister Beatrice are styled as Princesses and so it wouldn't be unusual if The Queen offered Jack a title - most likely an Earldom," Brookes said.

"Of course, it's down to personal choice as to whether he accepts it," Brookes continued. "If Jack was to accept a title - an Earldom, for example’s sake - he would likely be known as The Right Honourable The Earl of […]."

"Any children the couple have would take on subsidiary titles, a son known as Viscount and daughter, Lady. As is custom, we’ll likely find out on the morning of the wedding as to whether any titles have been granted/accepted," he added.

Princess Eugenie and Brooksbank are already busy with their wedding preparations. Sarah Ferguson is reportedly very involved with the planning. The Duke and Duchess of York are working together for the wedding reception which will be held at their shared home, the Royal Lodge.