She was the daughter of the Haarlem brewer Simon Gerrits and Guerte Koen Hasselaer. When the city was besieged by the Spanish, period diarists reported that all of the townspeople, man, woman, and child, fearlessly helped to rebuild the city defenses that had been destroyed by enemy cannon. One account written in Latin from Delft, mentioned Kenau by name as an unusually fearless woman who worked night and day carrying earth to the city walls to rebuild the defense line.