Sebald de Weert was born in
Antwerp, the sixth of 17 children of Johannes (Jan or Hans) Sweerts de Weert (b. 1538) and Clara (Claartje) Wonderer (1541–1595). The family soon (Jan 10, 1569) left Antwerp for
Cologne, in Hans' own words to escape the "tyranny and persecution". In 1575/6 the family moved to
Amsterdam, between 1579 and 1584 they were back in Antwerp, and by 1586 they lived in
 Sebald was originally employed as a ship's navigator with the VOC (in Middelburg?), and over the years worked his way up to vice
admiral in the Dutch East India Company. He signed his name "Sebalt", but had the official
Latinized name "Sebaldus", and has often been referred to in English and French as Sebalde de Weert, and in Spanish and Portuguese as Sebaldo de Weert.