Jaantje van Leeuwen was a daughter of Moses van Leeuwen and Flora Bloemekoper, who lived on the same address. She married 520792 in 1905 in The Hague. They divorced in 1912. They had a child that survived the war.
Haags Gemeentearchief, Overlijdensakten Den Haag, nr. C 416 (1950); Huwelijksakte 23 mei 1905
In addition, a Jokos file (number 21297) on this family is at the Amsterdam Municipal Archive. Access is subject to authorization from the Stichting Joods Maatschappelijk Werk.