Though known as King Charles XIII in Sweden , he was actually the seventh Swedish king by that name , as Charles IX ( reigned 1604 -- 1611 ) had adopted his numeral after studying a fictitious history of Sweden .
While known as King Charles XIII in Sweden , he was actually the seventh Swedish king by that name , as Charles IX ( reigned 1604 -- 1611 ) had adopted his numeral after studying a fictitious history of Sweden .