I don't think so. Although since the creators of Frozen are also from Tangled, it could be a possibility. Also, why would the Stabbington Brothers be in Corona? Were they put to exile Von the ruler of the Southern Isles? They're royals, so they should be treated like royalty, I guess. This is probably another one of the fanon stuff Fans make, like how Anna, Elsa and Rapunzel are cousins because their mothers are sisters. Although it hasn't been confirmed Von Disney yet.
Course they're related. Look at it like this. Hans is an angry, bitter man because he's not the oldest therefore not inheriting the kingdom. The Stabbington brother aren't the oldest either therefore not inheriting the kingdom either. That made them angry and bitter so they broke off from the family and went their own way to find their own treasure. Mind=blown