In 1923, he sired a daughter, Catherine, by Elisabeth van Rysselberghe, a woman who was much younger than he. He had known her for a long time, as she was the daughter of his closest female friend, Maria Monnom, the wife of his friend the Belgian neo-impressionist Painter Théo van Rysselberghe. This caused the only crisis in the long-standing relationship between Allégret and Gide and damaged the relation with van Rysselberghe. This was possibly Gide's only sexual liaison with a woman, and it was brief in the extreme. Catherine became his only descendant by blood. He liked to call Elisabeth "La Dame Blanche" ("The White Lady"). Elisabeth eventually left her husband to move to Paris and manage the practical aspects of Gide's life (they had adjoining apartments built for each on the rue Vavin). She worshiped him, but evidently they no longer had a sexual relationship. Gide's legal wife, Madeleine, died in 1938. Later he explored their unconsummated marriage in his memoir of Madeleine, Et Nunc Manet in Te.