Jan Koster was born 15 February 1861 in Hoogkarspel, North Holland, Netherlands to Hendrik Koster (1816-1883) and Antje Meester (1823-1905) and died 26 July 1951 Westwoud, North Holland, Netherlands of unspecified causes. He married Agatha Ruitenberg (1861-1923) 30 April 1885 in Hoogkarspel, North Holland, Netherlands.
Children
| Name | Birth | Death | Joined with |
| Hendrik Koster (1885-) | |||
| Jan Koster (1888-) | |||
| Pieter Koster (1889-1891) | |||
| Marijtje Koster (1890-) | |||
| Anna Koster (1893-1977) | 19 February 1893 Hoogkarspel, Netherlands | 28 January 1977 Bovenkarspel, Netherlands | Nic Tol (1888-1958) |
| Jacob Koster (1894-1914) | |||
| Alida Koster (1895-) | |||
| Martha Koster (1897-) | |||
| Johan Koster (1899-) | |||
| Johanna Koster (1901-) | |||
Siblings
| Name | Birth | Death | Joined with |
| Gerrit Koster (1844-1917) | 19 May 1844 Hoogkarspel, North Holland, Netherlands | 30 July 1917 Wervershoof, North Holland, Netherlands | Grietje Grent (1845-1927) |
| Maartje Koster (1847-) | |||
| Neeltje Koster (1853-1931) | 4 March 1853 Hoogkarspel, North Holland, Netherlands | 7 March 1931 Andijk, North Holland, Netherlands | Jacob Sijm (1846-1910) |
| Aagje Koster (1857-1892) | |||
| Name | Birth | Death | Joined with |
| Jan Koster (1861-1951) | 15 February 1861 Hoogkarspel, North Holland, Netherlands | 26 July 1951 Westwoud, North Holland, Netherlands | Agatha Ruitenberg (1861-1923) |
Residences
Footnotes (including sources)
| ‡ General |