What happened to little Richlieu?

In 1943, Vladek and Anja send him to live under the protection of Uncle Persis, where they think he will be safer. Richieu travels with Anja's sister, Tosha; Tosha's daughter, Bibbi; and Vladek's niece, Lonia. But soon after, Zawiercie is liquidated by the Nazis. Rather than be taken to the gas chamber, Tosha poisons herself and the children under her care, including Richieu.