admittedly this a very unlikely scenario, but let's say it goes ahead in 1710 when Charles XII was in the Ottoman court. They have a single son who survives through the normal dangers of childhood in the era. The family returns to Sweden in 1715 with Charles XII and Charles XII is still killed in 1718. The question now is, what will Sweden and Britain do with a personal union looming? While Louisa herself is ineligible due to her Catholicism, Charles XII would 99.9% raise the kid as a protestant, which means that the kid (let's name him Gustav for the sake of the thread) would have a senior claim to the British throne through his lineage to Charles I of England. Would a personal union take place? What would the implication of a surviving Zweibrucken Dynasty mean to both Sweden and northern Europe?