Sjouke Boonstra, born in Harlingen on December 2, 1839, son of Sije Sybes Boonstra and Marijke Jans Noordkamp, longshoreman, died before June 4, 1888, aged at most 48 years.

Sjouke was married in Barradeel on June 7, 1861, at the age of 21 to
Hijlkje de Vries (aged 21 years), born in Barradeel on September 22, 1839, daughter of Douwe Gerrits de Vries and Fetske Douwes Dijkstra, died before June 4, 1888, aged at most 48 years.

• 1 : Douwe Boonstra, born in Harlingen on April 5, 1862.
  

• 2 : Sije Boonstra, born in Harlingen on March 8, 1864, bloatercurer, dock hand, docker and transport worker, died in Harlingen on September 15, 1923, aged 59 years.
  Sije was married in Harlingen on June 4, 1888, at the age of 24 to Grietje Tigchelaar (aged 24 years), born in Harlingen on May 27, 1864, daughter of Klaas Gerrits Tigchelaar (dock hand, workman and dock hand) and Grietje Dirks Sleeper van Arum (maid-of-all-work), maid servant, died in Harlingen on December 6, 1954, aged 90 years.
  

• 3 : Sybe Boonstra, born in Harlingen on November 17, 1865.
  

• 4 : Hylke Boonstra, born in Harlingen on November 17, 1865, died there on January 4, 1938, aged 72 years.
  

• 5 : Hendrik Boonstra, born in Harlingen on December 29, 1867.