Friedrich II sent Hermann von Salza to the pope and, upon his return, received a marriage proposal. The intended bride for Friedrich II was Yolande de Brienne, hereditary Queen of Jerusalem, only twelve years old. 
The pope hoped it would encourage Friedrich II to go on crusade, but Friedrich was still reluctant. Hermann von Salza, who had also been a good friend of Friedrich II, needed all his pursuasive powers before Friedrich II would consent to the marriage. Moreover it was to take another two years before, by then, the thirty-one-year-old Friedrich II was married by proxy to the fourteen-year-old Yolande de Brienne. After the marriage ceremony had taken place, she was crowned Queen of Jerusalem. 
She then went to Brindisi where her father and the groom were waiting for her and, on 9 November 1225, another marriage ceremony took place. However, a day later Friedrich II left unannounced and Yolande's father, Jean de Brienne, followed him to find that Friedrich 
II had not only taken the title of King of Jerusalem but had also fallen passionately in love with a cousin of Yolande, writing charming love poems for "the flower of Soria". 
Jean de Brienne, who had been King-consort of Yolande's mother, had expected to keep the title of King of Jerusalem and went to the pope to complain. Nevertheless the marriage was consummated and Yolande gave birth to a son, Konrad, on 25 April 1228. However, on 1 May 1228, she died aged only sixteen. 
 

Source: Leo van de Pas