This chart shows the lineage starting with Willem Christian Pieter Jansz I. It also shows more family members then my mom Marie had in her records. I.E. Antonie, who as you can see died less than a month after birth. Then there is WCP II, named after his father and Helena Berendina, named after her mother finally Laurance Johanna. Mr. A. Jansz, you can see a Anthonie circled on chart A3, that could be him since he was born the same year as Bill, 1909. He was requesting info on Derks kids as you can see in the letter.

Helena Berandina Jansz van der Veer and Henriette Louise Jansz van der Veer married the brothers van der Veer and all went to Sumatra, Indonesia, Where Willem Marius van der Veer, Henriette's husband started a rubber tree plantation, and all four children and at least 2 grandchildren were born in Sumatra. I don't have any information on Kors as to his position at the plantation if any. You can see more information about the van der Veers here.