Considering that Gustav IV Adolf was forced to resign and driven to exile during a coup d'etat in 1809 and that the later Bernadotte family got into power after the death of Charles XIII, the brother of the king.
Who would be the Swedish king if the royal family had not been forced into exile by illegal means in 1809? Considering Sweden had primogeniture until 1980. I write illegal here since the coup was not issued by the Swedish parliament and thus can be viewed as such
Princess Sofia Wilhelmina (21 May 1801 – 1865). She married Grand Duke Leopold of Baden, and their granddaughter Victoria of Baden married the Bernadotte king Gustaf V of Sweden. (The present King Carl XVI Gustaf of Sweden is thus Gustav IV's heir.) Source
According to Wikipedia. However, it does not list all her children. If some child of hers or her sisters younger or older would be male, these children would hold a stronger claim than the present king. According to the laws before the coup by the army officers.