Furthermore, Claeys remarks that the chroniclers and genealogists of Azorean history based their writings on documents of the XVIth and XVIIth centuries, several generations after Willem's lifetime, maintaining the surname "da Silveira" for all the children of the first marriage and even for Willem himself. This would probably mean, in Claeys' conclusion, that the first seven children are not from Margarida de Zambuja, and thus retain their mother's name (in Bruges, they were probably named De Kersemakere), while Francisco, the youngest, was always called Casmaca. Claeys' also claims that, according to the Flemish and Portuguese customs, men never receive the surname of their wives, thus, the denomination "Willem van der Haegen" would be incorrect.