This is a fan theory I have connecting Big Hero 6, Frozen and HTTYD. Please read and review.
Fred is a descendant of either Hans or one of his brothers. This is based on the fact his parents are rich, and that he has a statue of Hans in his back yard. (The statue Baymax blew up with his fist when trying out his new suit.) Between the times the story took place, one of the brothers moved out of the castle and took his inheritance with him. Instead of spending it on everything he could, he opened a business. As time went on, Fred's ancestors slowly made their way to Japan taking advantage of new markets opening up.
Fred is Tuffnut's reincarnation. This is based on the fact Fred wants the ability to turn himself into a giant fire breathing lizard at will. Part of him remembers the comfort and security that Belch gave him and wants that feeling back. And the fact Fred's not all the bright.
I hope it made some sense. I'm not good at making sense sometimes and all my friends liked my theory so I hope you do to. Anyway thank you for reading and please review.