Sije Sybes Boonstra, born circa 1812 (?).

Sije was married to
Marijke Jans Noordkamp, born circa 1816 (?).

• 1 : Sjouke Boonstra, born in Harlingen on December 2, 1839, 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.