I believe that you may have two Losee families combined.
1.Lawrence Losee, baptised 18 Oct 1705 at Jamaica Reformed Dutch Church, son of Simon Losee and Grietje Koeck.He married, probably in Fishkill, Dutchess County in 1730, Rachel Delange (De Long) baptized 11 April 1708 in the New York Reformed Dutch Church, the daughter of Frans Langet (De Long) and Maritje Van Schaak of Kingston, Ulster County, NY.
2.The best research I have been able to discover does not include a son Cornelius nor having the family living in Westchester County.It is true that White's work has a Losee family in Westchester County.
3.Dutchess County records place Lawrence and Rachel in Dutchess County during the years 1730-1784.
4.Cornelius Losee bp. 29 May 1705 Brooklyn married Deborah Langdon in 1727 at Hempstead, LI, NY.They had several children born at Hempstead and Dutchess County.
5. See: NYGB Record, Vol 9- Records of St. George Church, Hempstead. Fishkill Reformed Dutch Church records complied by Worden Settlers of the Beekman Precinct by Doherty Baptisms, New York Dutch Church 1639-1730, NYGBS Will of Simon Losee, Liber 24, p. 201 Jamaica Reformed Dutch records, NYGBR, Vol 105 Seversmith Early Settlers of Bushwick by Provost Kingston church records edited by Hoes