Appointed guardian of the children of Jacob Bellart

Two months before his death on 6 June, 1689, Jacob Bellart (Bellard), substitute sheriff who lived on the east side of the Voorstraat, named Leonard van der Houck, a medical doctor, and Leeuwenhoek as the guardians of his underage children, whose mother was Sophia van der Sleijde. In 1689, Cornelis was 22, Johanna was 20, Henricus was 17, and Margarita was 14.

The notary was Leeuwenhoek's nephew Adriaan Leeuwenhoek, who handled the Bellard estate in five separate documents.

• 1689-04-23 Leeuwenhoek named as guardian of Bellard's children (ONA inv. 2426, fol. 317-318).

• 1689-06-27 Leeuwenhoek as guardian approved of the sale (by auction) of Bellard's property, a garden and little house in Vrijbaan, outside of the Schoolpoort. Johannes Ortwinius bought it for 875 gulden, 4 stuivers (ONA inv. 2426, fol. 394-398).

• 1689-07-08 Leeuwenhoek noted as guardian in the inventory of Bellard's estate. He owned several properties and had many creditors (ONA inv. 2426, fol. 414-446).

• 1690-03-09 Leeuwenhoek noted as guardian in the Johanna Bellard / Gillis Vileers marriage contract (ONA inv. 2427, fol. 188). They were married on March 29 (DTB Trouwen Inv. 14.77) and had a daughter, Sophija Cornelia, the following December (DTB Dopen Inv. 14.59) and a son, Albertus, a year after that (DTB Dopen Inv. 14.12) and then five daughters in the following eight years, at least two of whom died as babies.

• 1695-07-22 Leeuwenhoek noted as guardian in the Margareta Bellard / Willem Wardolen marriage contract (ONA inv. 2429, fol. 1086). They were married later that month (DTB Trouwen Inv. 14.78)