 Hendrika van Leeuwen was the sister-in-law of Gunnar Nordström, known as the "Einstein of Finland", who studied in Leiden with Paul Ehrenfest, the successor of Lorentz.Her sister Cornelia (Nel) also started a PhD in Leiden, under Willem Keesom, but stopped when she married Nordström and moved with him to Helsinki.Van Leeuwen was present at the celebration of the golden anniversary of the doctorate of Lorentz, on 11 December 1925,
and on that occasion reported on the role of Lorentz as scientist and teacher.