Who is Willem van Doorn from The Covenant and what is their importance?

Willem van Doorn is Mevrouw's son. Willem grew up in Java until at the age of fifteen, at which time, his mother put him on a ship with his older brother Karel, who is sent to help the locals with the transition of Portuguese to Dutch rule over the fort at Malacca. From there, the governor at Java tells Mevrouw van Doorn that for her sons to advance, they should be seen at head office - particularly Karel who has aspirations of being governor of Java one day. Willem is afraid to go to Holland, and when their ship wrecks off the Cape of Good Hope, he sees his opportunity to stay behind and does.