↑ Thomas Curtis Van Cleve's The Emperor Frederick II of Hohenstaufen: Immutator Mundi (Oxford, 1972). Page 381:"Certainly there is some evidence that a son, Jordanus, was born in the year 1236, and died shortly afterwards, but the only son of Frederick II and Isabella of England whose birth can be firmly established was a second Henry, born in 1238, and named after his uncle, Henry III, the King of England." Ref supplied by Peter Stewart via soc.gen.med 20 Jan 2008
