sentences:  Petrus Jozef Sietse de Jong was born on 3 April 1915 in Apeldoorn in the Netherlands province of Gelderland in a Roman Catholic family that originated from Friesland, as the sixth of seven children of Joännes Jans de Jong (24 February 1878 – 28 November 1931), a railroad superintendent, and Gijsberta Adriana Schouten (29 December 1877 – 30 June 1957).After leaving secondary school, de Koninklijke Hogereburgerschool (now de Koninklijke Scholengemeenschap), he joined the Royal Netherlands Navy as a midshipman in 1931 and subsequently attended the Royal Netherlands Naval College in Den Helder.In 1934, he received his commission as a Sub-lieutenant.