Klaas de Groot, born in Wier on July 15, 1837, son of Dirk Klazes de Groot (worker) and Pietje Leenderts van de Akker, worker, died in Arum on May 28, 1918, aged 80 years.

Klaas was married in Wonseradeel on May 8, 1869, at the age of 31 to
Jeltje Robijns de Jong (aged 32 years), born in Lollum on June 22, 1836, daughter of Robijn Jans Arbeider (worker and worker) and Saackjen Gialts Kooistra, died after May 28, 1918, aged at least 81 years.

• 1 : Dirk de Groot, born in Pingjum on February 2, 1870.
  Dirk was married before February 1, 1901, at the age of at most 30 (1) to Christina de Vroom (aged at most 31 years), born circa 1870, died in Zaandam on February 1, 1901, aged approximately 31 years.
  Dirk was married in Wonseradeel on March 4, 1903, at the age of 33 (2) to Johanna Tuzee (aged 33 years), born in Groningen on April 20, 1869, daughter of Jan Tuzee and Geertruida Steenhuis, kindergarten keeper.
  

• 2 : Klaas de Groot, born in Pingjum on March 25, 1876, worker.
  Klaas was married in Wonseradeel on May 28, 1898, at the age of 22 to Sijke Goslinga (aged 21 years), born in Pingjum on November 26, 1876, daughter of Tjerk Goslinga (worker) and Janneke Kuipers, maid servant.