The Heetvelde family was an influential patrician family in Brussels who were members of the Brabant nobility. During the reign of Duchess Joan, Thierry van den Heetvelde, the head of the house, was found murdered and suspicion fell on Nicolas de Zwaef, one of the leaders of the Sleeuws lignage, who was publicly charged with the crime by Thierry's sons. Zwaef's family claimed he was falsely accused. Tensions ran high as Jean van Lombeck of the Sweerts lignage, the same to which the Heetveldes belonged, had been previously assassinated at the end of the 14th century. The other lignages aligned themselves with one or the other party and a bloody feud arose that lasted 20 years. Duke John IV mediated; however, as a friend of Zwaef, his sentence banishing the Heetvelde sons, delivered in 1420, was met by an appeal by the latter to the Estates of Brabant, which quashed the ruling. Furthermore, they informed the duke that no aid would be extended to the sovereign until their grievances had been met. John's inability to do so helped spark the rising of 1421.
Historical Dictionary of Brussels. Paul F. State.