Jan Henryk Ferdynand Sosnowski (1896-1959), born in Paris, son of Kazimierz Marcin Sosnowski and Helena Goldszpiegel, engineer. Naturalised in France on 1 January 1900 (AdP AN Paris 17e no. 1186 of 1899).

On 24 July 1920, he married Janina Livet-Karwowska. An entry in the newspaper Polonia No. 33 of 4 September 1920 states: 'Nuptials. On 24 July, in the closest family circle, the wedding of the young engineer Mr Jan Sosnowski, son of our illustrious countryman Mr Kazimierz Sosnowski and his wife, Doctor of Medicine Sosnowska, took place with Miss Janina Livet-Karwowska, a medical student, daughter and granddaughter of the Karwowski family of merit to their country and to emigration. We send our best wishes to the newlyweds' parents.

Janina Livet-Karwowska, born 15 April 1899 in Warsaw, daughter of Louis Joseph Livet, writer, and Hedwige Rosalie Félicite Karwowska (AdP AN Paris 17e no. 1186 of 1899, transcription from the French Consulate in Warsaw), died 22 December 1991 in Sèvres (Hauts-De-Seine) (INSEE).

Jan Henryk Ferdinand Sosnowski died on 19 March 1959 in Paris at his residence, 13 rue Clément Marot (AdP AD Paris 10e No. 140 of 1959).