Seems kinda dumb to marry off your sister to the family you KNOW dislikes you and has control over the largest/strongest military in the country. That's like asking for them to usurp you.
They were already trying to plot a rebellion using the king's cousin, but now they have his sister under their control, so it would be super easy to just rebel with her as the potential "rightful ruler." It's even better if she's actually a "half-wit" so they can just manipulate everything behind the scenes and control the country while she's just a figurehead with no real power.
Or, if they are worried about her erratic behavior making them look bad in front of people, they can just make her have a child with the ML, and then use the child as an excuse to rebel and put the kid on the throne (and control the throne as regents while the kid grows up). It seems like it was known that the FML was normal before she was traumatized by seeing her family murdered, so it's not like they have to really worry about the kid also having behavioral issues due to genetics or anything.
Okay I can see where this is going now. OG!FML was a a young dragon experiencing living as a human, so that's why her memory of being a dragon was sealed. I'm predicting that the OG!ML was also a dragon experiencing living as a human too, and is probably the badger. I'm guessing his badger time will end (possibly due to him "sacrificing" himself to save the princess from danger) and he'll start his human life with his memory erased, but he'll still have subconscious feelings towards the princess. He'll end up falling in love with her and eventually remember he's a dragon and save her from the curse. Completely just my guesses, but I've read so many isekai stories I feel like I know where this is going lol
Who's the OG!FML?? (Yea I forgot like yea)