Ragnar's (Travis Fimmel) reign over Kattegat might be challenged by one of his own sons when "Vikings" return for season 4.

During the midseason finale, viewers of the historical drama series saw that Ragnar and Aslaug's (Alyssa Sutherland) children already grew up to become fine young warriors. But this means that one of them is fit enough to fight their father to sit on the throne.

Jordan Patrick Smith, the actor who portrays the role of Ragnar and Aslaug's eldest son Ubbe, revealed that the youngest brother Ivar the Boneless (Alex Høgh Andersen) has the potential to beat all of them to overthrow Ragnar as the King of Denmark.

"Even though he's the younger brother, we would look up to him for the Viking he is and how strong-willed he is," the actor said in an interview with IGN. "He has one of the biggest disabilities you can have as a Viking where you can't walk, but he's still smart enough and strong enough to keep going."

Andersen also believes that his character is bound to have an amazing future up ahead.

"Ivar is strong and determined and independent, and you need that if you have to take over the world later on," the Danish actor stated.

Meanwhile, hairstylist Dee Corcoran teased that Ragnar's ex-wife Lagertha (Katheryn Winnick) will have a new look for the second half of season 4.

"This season you'll see [Lagertha] with little pieces of Celtic metal [in her hair] when she's going to battle, which looks fabulous on her," the stylist told International Business Times.

Corcoran also mentioned that they also transformed Linus Roache's character King Ecbert of Wessex by making him age significantly for the upcoming episodes of season 4 because of the huge time jump.

History Channel is expected to announce the official release date of the midseason premiere of "Vikings" season 4 in the coming days.