 When his father was killed in battle in 1617, the Admiralty of Zealand appointed all five of his sons as Lieutenant, including Cornelis (or "Kees") and his oldest brother Johan, despite their young age.This exceptional favour was granted in recognition of the great merits of the father and of course prevented his family from becoming destitute.In 1626 Cornelis is first mentioned as actually serving on sea, during a privateering raid.