I married Princess Rosario for status and to make sure power fell into the hands of a noble leader, but my true love remained Hartmann. Just like how (spoiler alert) Paul marries Princess Irulan, but his heart belongs solely to Chani.
If you want to know how to do this. You need to go to the winter ball with Rosario and then go to the spring festival with Hartmann. At least I think.
Anyway. Shoutout to Harris Powell-Smith for making the story.