Claims have been made Prince William didn't exactly give brother Harry his blessing to marry Meghan Markle.
The Mail on Sunday has reported that in the lead up to the royal wedding in May, William voiced his apprehension.
An alleged friend of William's told the news outlet, "The problem is that the Cambridges felt things had moved very quickly between Harry and Meghan.
"Wills particularly was worried and felt close enough to Harry to voice his thoughts," William's friend told the Mail on Sunday.
William reportedly raised his doubts with his grandmother, the Queen, too.
The Sun reports Harry was offended by William's comments, stood up for his wife to be, and obviously did not take on board his brother's concerns.
He expressed disappointment and felt William wasn't making an effort to welcome Meghan into the royal family following their engagement, it is claimed.
The source told The Sun, "Harry felt William wasn't rolling out the red carpet for Meghan and told him so."
William's alleged apprehension has come to light in conjunction with rumours of a tense feud between the Cambridges and the Sussexes.
Rumblings of discontent between the young royals can be traced as far back as a bust up at Christmas last year where Kate reportedly attempted to explain the rules of the Monarchy to Meghan, a move which, according to The Sun, she didn't take very well.
Other incidents between the duchesses have since been reported, such as Kate scolding Meghan over the way she spoke to a member of Kate's staff.
"Her and Kate fell out when she b*****ked Kate's staff. Kate said, 'That's unacceptable. They're my staff and I speak to them.'"
And The Sun reports Kate's concerns have echoed William's as she told friends she was very sad about what was happening and felt her brother-in-law was "changing".
From the beginning, Meghan has been noted as a strong character. But so is Kate. So reports of clashes between the sisters-in-law aren't surprising among the royal inner circle.
Since the death of their mother, the princes have been recognised for their special brotherly bond in the public eye. It certainly appears their relationship could be falling apart. This year, the royal couples will spend Christmas apart.
News of unrest began following reports Harry and his pregnant wife are leaving Kensington Palace for Frogmore Cottage in the grounds of Windsor Castle.
While rumours of a rift between the families continue to swirl, Kensington Palace remains silent on the issue.