All the following info was sent to me by Sherron Westerfield (sherronw@searnet.com).
After his father died, his mother married 2d Theunis Jansen Van Ammak, who then became Jacobus' step-father. A month later, Theunis became his father-in-law when Jacobus married Theunis' daughter, Aefje Ammak. Mother and son married father and daughter!
Jacobus Cosine is on "A True List of the Respective Officers and Souldiers Belonging to the Regiment of Militia in Kings County; 1715," in Capt. Frances Titus' company.
"Jacobus Cozyn" is listed in 1738 on "A List of all the Inhabitants of the Township off Flattbush both of Whites and Blacks, Males and Females." He and another white male above 10 years were living with 2 white females above 10 years, 2 black males above 10 years, a black female above age 10.