Disney theory

Disney have a reputation for including their characters in a number of their own films, such as Scar from the lion king, showing up as a cape in the film Hercules, or Sebastian from the Little Mermaid being pulled out of a trunk in Aladdin; when Genie is going through his rule book. The fact that they are included in some way, it is safe to assume that disney want to connect their films and keep them in the same 'universe' so to speak.
Disneys Frozen is the latest masterpiece to grace our screens and the tradition has not stopped as  Rapunzel from Tangled appears twice. Once when they open the gates to the castle and again at Elsa's coronation ball.  But before they actually appear Anna and Elsa's parents have to travel overseas and them being King and Queen suggests that the trip is probably important and it is not just a personal holiday. This got me thinking if the makers of Frozen wanted to connect these two films, I think they may have done just that but in one more way. Tangled ever after is an animated short set after the film Tangled and features Rapunzel and Flynn's wedding, it is also made clear at the very end of Tangled that a substantial amount of time passed before Rapunzel and Flynn even got engaged.
For a royal wedding it is also safe to assume that other members of royalty would be in attendance to said wedding, probably reigning monarchs from other countries who would have had to travel quite a way. So it is possible that this could be the event which prompted Anna and Elsa's parents to leave Arandale and travel across the ocean which resulted in their death.
Some people may think that I am reaching in this theory but quite honestly it isnt any less implausable than some of the other thepries floating around online.