can somone help me with my fanfic please?

I'm making a fanfic that at one point involves the villain who is a prince to try and marry and princess of another land so that he can rule her land and after they marry he plans to kill her. So I was wondering, if a prince and princess of different kingdoms marry and one of them dies before producing an heir, would the living spouse still have control of the dead spouse's kingdom?
Sorry, I know this is a stupid Вопрос but it'll really help me with my fanfic thanks!