When Caspar and Claessie were married in the winter of 1677-78 in Rotterdam, Claessie was a widow. She had a son Isaack from her earlier marriage to Pieter Cornelisz Groen whom Claessie had married in the winter of 1664-65 in Rotterdam. Witnesses to Isaack’s baptism on 3-11-1666 in Rotterdam were Jan Isackx van Leeuwen and Sara Claes. They were Claessie’s parents and had been married on 8-10-1641 in Rotterdam. Sara Claes was a widow of Louris Jansse van Ceulen, whom she had married on 16-12-1636 in Rotterdam.
Jacob van Os departed on 10-5-1712 from Rotterdam as a sailor on the ship "Huis ten Donk", build in 1711 in Rotterdam with a length of 130 voet (9 meters). The ship docked on February 17, 1713, in Cape Town. On April 3 the ship continued its voyage to Batavia in Indonesia, arriving there on July 4, 1713. I can’t trace Jacob van Os in any other voyages for the Dutch East India Company.