There's really been a whole lot of speculation that something is amiss and wrong between the brothers and their spouses because it seems to be the one that the press is stoking the fire with. Its what it *looks* like right now. As royal watchers, we've reveled in seeing Harry and William joke about each other and tease each other and then there were three of them when Kate joined in the mix. All was well and that's what we were used to seeing all the time.
Personally, I have a theory that the culprit playing into this discord is nothing more than the word *transition*. The transitioning of all four main players into the world of being full time working royals. The transitioning of all four players into streamlining their own households, roles and incentives to carry into the next reign. Both couples have their own families and their own residences that suit them. All the ducks are quacking as they line up in a row ready to transition easily into the next reign.
When was the last time any of us saw Edward and Andrew do things jointly? Or Anne and Charles? Or Sophie and Kate. None of these happen very often (if at all). Individually, they can cover more ground and causes and engagements without teaming up. I do believe its all the machinations with "The Boss" directing traffic as she assigns more and more duties to Charles and has entrusted her precious Commonwealth to Harry and Meghan and William is getting more and more involved in the Duchy of Cornwall affairs.
Things are changing but I don't believe that there's a "personal" reason between the two brothers that is causing it. The "Firm" is a well oiled and smoothly running corporation and its "Boss" has been busy behind the scenes and seeing as this "Boss" was once a Girl Guide, I think she took their motto to heart. "Be Prepared" When the time does come for Charles to take the throne as King, everything is going to be in place for a smooth transition.
So that's it in a nutshell for me. Its easy to imagine a "feud" or a "split" or a "parting of ways" in the here and the now between the brothers but things aren't always as they seem to be and we, the public, and even the press aren't in the loop of just why things happen the way they do sometimes.
I'm going to just keep watching and carrying on.