Hello everyone! So This is a bit of a clarification page. I notice I haven't been very clear at all.
Alfred and Sakura were in a relationship for almost a year when in actuality she used Alfred's and her own feelings for him to better the interests of her country.
Ludwig feels that his brother's motives are too rash and has different plans for running and bettering the kingdom of hearts. He isn't a bad person, he is just doing what he feels would be best for his kingdom.
The night of Alfred and Arthur's marriage, Alfred did not bed Arthur. They haven't grown close enough and Alfred wants to make sure everything is okay with his queen. There isn't a prophesy that makes them fall in love, but rather it's suggested that they should because of fate.
Gilbert took Roderick because he took Eliza. :).
I hope this clears things up! Ouo