Andrée had made many extended visits to Biarritz during her father's illness. After he died, she was intent on preserving everything related to his artistic career. She carefully crated up the entire contents of his atelier at "Villa Pat". Since she would be staying with her widowed mother in Biarritz for a while, she shipped the crates to Paris for safekeeping in the temporary custody of two trusted nephews, the noted architects Édouard Niermans (1903–1984) and Jean Niermans (1897–1989), "Officier de la Légion d’Honneur" (:fr:Jean Niermans). Their father, Édouard-Jean Niermans (:fr:Édouard-Jean Niermans) (1859–1928), celebrated as the architect of the "Café Society" and "Chevalier de la Légion d’Honneur", married Dewis's sister, Louise Marie Héloïse DeWachter (1871–1963), in 1895. Dewis was very close to Louise and in her home the artist socialized with the likes of Auguste Renoir and Jules Cheret.