Spoilers for The Royals episode "Forgive Me This My Virtue" follow. Just when it seemed like things were improving for Liam, he gets hit with another personal blow. Kathryn tries to kiss Robert on The Royals during the April 22 episode. Even though he just became engaged to Willow, it seemed that Robert was interested in rekindling his romance with his ex as well. But instead, the king manipulates Kathryn into revealing her feelings for him while Liam is in earshot. It's a dirty move, but it's better that Liam knows Kathryn's true feelings now rather than continuing to be in a relationship with her. Based on how quickly Kathryn betrays Liam, it could be possible that something else is at play here. But if that's not the case — well then, you can kind of understand why Kathryn calls herself a "bad person."
While Robert is a tricky guy, he seemed genuine when he gave Liam his approval to date Kathryn again in Episode 5, "There's Daggers in Men's Smiles." The king told Liam, "You have my blessing. Please, pursue her." After all, he had moved on with Willow. But when he had to face Liam and Kathryn at Helena's birthday dinner during Episode 6, "My News Shall Be The Fruit To That Great Feast," his resentment showed. And even though it's hard to feel bad for Robert, you might have felt for him since his brother had slept with Kathryn while he was stranded on an island and then kept it a secret from him.
That empathy was short-lived though since Robert approached Kathryn alone in the hallway in Episode 6 and said, "I'm glad you came tonight." And his actions are even more infuriating in "Forgive Me This Virtue" since he propositions Kathryn with a secret rendezvous — and she accepts. All on the same day where both Robert and Willow's engagement and Liam and Kathryn's relationship went public.
Maybe Kathryn's plan in dating Liam was to get closer to Robert all along. Or maybe Willow's slightly nasty comments pushed her over the edge. But she chose to go to Robert's room and say she wants Robert, so whatever her motivation, it doesn't look good for her. Originally, it almost seemed that Kathryn engaging with Robert might have been her way of trying to show Willow what a bad guy Robert is. But when Liam catches Kathryn with his brother, she looks incredibly guilty — and Liam looks utterly crestfallen.
Liam immediately snaps at his brother since it seems like Robert had intentionally taken away something of his again. And knowing that it was Robert's plan to show Kathryn's true colors explains why he smirked a bit after his discussion with her in "My News Shall Be The Fruit To That Great Feast." Robert possibly had this plan in mind when he encouraged Liam to go after Kathryn, which would be pretty manipulative and sad for these siblings. But Liam takes Robert exposing Kathryn's betrayal as a sign that his brother is there for him.
Liam's feelings toward Robert have shifted dramatically since the beginning of this season. And so perhaps you're suspicious that Liam could now be aligning himself with Robert. Yet, with their father's memory surrounding them during King Simon's Legacy Exhibit gala, it isn't unbelievable that Liam is trying to stand with his family. What's maybe more suspicious is how quickly Kathryn went from seemingly being happy with Liam to going back to Robert — who, at the end of Season 3, had slept with her, called her a derogatory term, and then dumped her.
Because of the speed of her betrayal, there is a chance that Kathryn has a plan up her sleeve (a sleeve that is nonexistent in all of her gorgeous backless gowns). It does seem odd that she just chose to get back with Liam and then so easily folds under Robert's smarmy charms. Especially since in "There's Daggers in Men's Smiles," she calls Liam "the good brother." But who knows? Maybe Kathryn has a thing for bad boys.
For now, Kathryn is the bad guy since she broke Liam's heart. And Liam seems open to having a relationship with Robert for the first time since Robert has returned — which, depending on how evil you think Robert is, could be bad or good. But with only three episodes left this season, there may be more to why exactly Kathryn decided to play with the hearts of these two royals again.