In an earlier post I identified the following facts concerning Jacob Cornelis' sister Tryntje.

1) Tryntje married Jacob Laufer on 17 Aug 1787.  Jacob died in 1807.
2) Tryntje married Hindrik Jans on 27 Sept 1807.

With her union to Jacob Laufer she had the following children:

1) Abraham - 10 May 1788
2) Hindrik - b. 8 Jun 1790; d. 19 Mar 1856
3) David - 28 Apr 1792
4) Tryntje - 4 Apr 1794
5) Annigje - b. 10 Nov 1803; d. 6 Feb 1838

Hindrik Laufer, a farm worker, married Geertje Berends on 29 Aug 1813 at Groningen.  He remarried Antje Hindriks Klaassen on 16 Sept 1841 at Groningen.  At that time Hindrik worked as a merchant.  Hindrik died on 19 March 1856 in Groningen.

David Laufer, a worker, married Jan Renjes de Graaf of Kloosterburen, on 18 May 1826 at Leens.

Annigje Laufer married a soldier named Egidius Nicolaus Madyol on 1 Dec 1822 at Groningen.  Bore Antje Madijol on 4 Jan 1825 at Groningen.  Bore Catharina Madijol on 25 Feb 1828 at Groningen.  Bore Pieter Madijol on 22 Mar 1831 at Groningen.  Bore Joanna Madijol on 3 May 1834 at Groningen.  Annigje died on 6 Feb 1838 at Groningen.