ET spoke with royal biographer Andrew Morton to discuss the upcoming May 6 coronation.
"Prince William will have a central role in the coronation, he will be pledging his loyalty to the king," Morton explained, noting, "Prince Harry will be back at the church. He's got a non-position."
Speaking of the service, Morton is curious to see how Prince Harry interacts with his family members. "It will be interesting to see, when they walk down the aisle, whether Harry bows to his father and to the queen, whom he's not had many kind words for."
Morton notes that despite the family being fractured, the coronation is an official state ceremony, not a family reunion. So, he believes that the royal brothers will act "with majesty."
"This is a state occasion, not a family occasion. It's not a day for reconciliation, it's a day to confirm the head of state," he said.
Earlier this week, William's very important role at his father's coronation was announced.
According to the Liturgy of the Coronation Service, the Prince of Wales will pledge his loyalty and allegiance to the king during the ceremony at Westminster Abbey.
William, 40, the heir to the throne, will kneel before his father -- after he is officially crowned -- place his hands between the king's and recite the words also known as the Homage of Royal Blood. "I, William, Prince of Wales, pledge my loyalty to you and faith and truth I will bear unto you, as your liege man of life and limb. So help me God."
William is the only royal who will honor the king in this way during the ceremony.
So why is it paramount that Harry attends the coronation without having a major role in the service?
Ahead of the coronation, ET got some insight from royal correspondent Omid Scobie about the importance of Harry's attendance despite the rift between him and his family members.
"He's the son of King Charles III, a man who he still respects and has a great adoration for despite the fractures in their relationship," said Scobie of Harry, who is attending without Meghan or their children. "But he's also fifth in line to the throne and a Counselor of State. So, it's important for him to be here in a constitutional position, regardless of how he feels about his family. But I hear from sources, he is looking forward to being a part of this moment despite things of the past that have happened."
Prince Harry's journey back to England for the coronation will be his first time being face-to-face with his family since the release of his bombshell memoir, Spare. However, it most certainly won't be the first time that he's spoken with some of them.
"Harry's had several conversations with his father over the months since the release of the book, largely about the coronation itself," Scobie said.
As for Harry and William's relationship, however, Scobie says nothing's changed in the matter. It's still as icy as ever.
"It's been stone-cold silence between the two brothers and that's continued since the queen's funeral through the release of the Netflix series, the book, and, of course, now this trip to London," the royal correspondent said, "and I don't think things will change."