 About three months later , he met Emperor Frederick 's son Henry in Metz and visited Henry 's guardian , <unk> , Archbishop of <unk> . From Germany John went to southern Italy , where he persuaded Pope Honorius to allow Emperor Frederick to postpone his crusade for two years . Frederick married John 's daughter , Isabella ( who had been crowned queen of Jerusalem ) , on 9 November 1225 . John and Frederick 's relationship became tense . According to a version of Ernoul 's chronicle , John got into a disagreement with his new son @-@ in @-@ law because Frederick <unk> a niece of Isabella who was her lady @-@ in @-@ waiting . In the other version of the chronicle John often " <unk> and <unk> " his son @-@ in @-@ law , who concluded that John wanted to seize the Kingdom of Sicily for his nephew Walter IV of Brienne and tried to murder John ( who fled to Rome ) . Frederick declared that John had lost his claim to the Kingdom of Jerusalem when Isabella married him ; he styled himself king of Jerusalem for the first time in December 1225 . <unk> of Sidon , Simon of <unk> , Archbishop of Tyre , and the other Jerusalemite lords who had escorted Isabella to Italy acknowledged Frederick as their lawful king . 
