2 ‘This Is Us’ Theories to Explain that Surprising Randall-Kevin Twist

*Warning: Spoilers ahead*

Not only did the latest episode of This Is Us serve up a seriously depressing look at Rebecca’s (Mandy Moore) forthcoming Alzheimer’s diagnosis and Kate (Chrissy Metz) and Toby’s (Chris Sullivan) marital woes, but it also featured a flash-forward that hints at a fight between Kevin (Justin Hartley) and Randall (Sterling K. Brown).

How do we know? Well, after the cops bring Rebecca home to what’s presumably Kevin’s new rustic lodge, she asks him if Randall is on his way to come to celebrate the Big Three’s 40th birthday. Frustrated, Kevin tells her that Randall will not be attending because they’re not speaking. Nine months earlier, at Thanksgiving, Randall and Kevin seemed to be on fantastic terms. So, what happened? We have two theories.

Theory 1: Sibling Rivalry

Kevin has long resented Randall for being closer to Rebecca. They understand each other in a way that Kevin and Rebecca don’t. Since Randall knows about Rebecca’s memory loss and doesn’t mention anything to his siblings, this could cause tension between him and Kevin. Judging from the episode ten promo, it also looks like Randall is the only sibling to go to the doctor with Rebecca and Miguel (Jon Huertas) and in the flash-forward Kevin and Kate seem well aware of Rebecca’s diagnosis. That said, it appears likely that Kevin is angry at Randall for hiding such major news from them.

Theory 2: Clashing Personalities

Another potential reason for their fight? Randall is very much a traditionalist and it seems like Kevin and his new pregnant fiancée probably moved pretty fast. It’s possible that Randall tried to tell Kevin to be careful with his new love and Kevin reacted defensively.

Guess we’ll have to wait and see when This Is Us returns with season four, episode ten on Tuesday, January 14, at 9 p.m. PT/ET on NBC.

RELATED: Every ‘This Is Us’ Season 4 Recap