He is married to Hiltje de Vries.
They got married on June 3, 1933 at Dantumadeel, Friesland, Nederland, he was 25 years old.Source 3
grandparents
parents
brothers/sisters
children
Sietze Koster | ||||||||||||||||||
1933 | ||||||||||||||||||
Hiltje de Vries | ||||||||||||||||||
Geboorteregister 1908, Kollumerland c.a.
https://www.graftombe.nl/names/info/195149/koster
Huwelijksregister 1933, Dantumadeel