In 1627, De With married for the first time, with his second cousin Maria de With from Nieuwenhoorn. In April 1628, their first child, Cornelis, died. The same year, De With, entering the service of the WIC, became flag captain on the Amsterdam to Admiral Piet Heyn during an expedition from 20 May to capture the Spanish treasure fleet. In September this attack was successful near Cuba. On 10 January 1629 the fleet returned to the Republic. Out of the bounty of eleven million guilders, De With was granted about 500 guilders, with which he was very dissatisfied, as he imputed to himself a crucial role in the capture by taking a barque in August, the crew of which provided essential information regarding the whereabouts of the treasure fleet.
