Jacobus, known as Koos, was a great friend and inspiration to the editors of this website. He assisted us via the internet from his home in Kloosterburen with his wife, Bernarda. Koos passed away in Winsum (Groningen) in 2025.

He provided much detail for the Halsema line in our genealogy database and provided much of the information on Kloosterburen and especially its Catholic Church, St Willibrordus, which you can find on these pages.

Since 1998 Koos was an inspiration to the editors of this website, he is our third cousin, and we are proud to call him our friend. May he rest in peace.

Thank you Koos! –halsema.org editors.