Because of her brother Manfredo's friendship with Emperor Friedrich II, the whole Lancia family had moved by 1230 to Sicily where her brother Manfredo remained constantly at court. At this time Emperor Friedrich II was forty-seven and a widower. In 1232 he fathered a son by Bianca Lancia, about whom nothing is known except that she also gave birth to a daughter, Constance, and was involved with the Emperor for sixteen years. 
Indeed, so little is known of Bianca that it is not even certain that Manfredo the elder was her father, for there is the possibility that there were two Biancas, mother and daughter, the first being 
Manfredo the elder's daughter. This would explain the difference in age of Manfredo the younger who would then be her uncle and not an elder brother. 
Many historians are convinced that---after the death of his third wife, Isabella of England---Friedrich II then married Bianca. It is significant that their son, Manfredo, is the only one of his illegitimate children mentioned in his will. Apart from a third wife for Friedrich II, there had been other mistresses besides, with the influence of Islam in Sicily at the time, the famous odalisques of his harem. Yet nothing affected their relationship. Their son, Manfredo, was not only the nearest and most favoured of the Emperor's children but was present when the Emperor died. The Emperor also remained a close friend with Manfredo Lancia the younger. It is not known when Bianca died other than that she survived the Emperor. 

Source: Leo van de Pas