Helpful published sources for this connection are (1) John E. Stillwell, MD, "Historical and Genealogical Miscellany - Data Relating to the Settlement and Settlers of New York and New Jersey," 1932, vols. 2 and 5, and John Osborne Austin, "Genealogical Dictionary of Rhode Island", 1887.
Austin cites Thomas's will, proved Nov. 22, 1675: "To sons Thomas, John and William, farm which I now dwell upon, equally, as each arrives at age, the dwelling house to be for son William, and his share of land to be adjoining house with orchard included. The farm not to be sold except among brethren, that is to say Thomas, John, James, William and Cornelius. To son James, land at age. To son Cornelius, land on west side of Seven Mile Lane, and if James and Cornelius die without issue, their part to brothers. If there be more divisions than one of land west of Seven Mile line, then my right in second division to son Gershom, and to him 10s [shillings]...."
Austin does not record any information relating to Gershom other than the Jan 27, 1667 entry, "He was to be apprenticed to Nathaniel Mowry till of age." Stillwell, however, says, of Gershom, "He was unquestionably the founder of the Monmouth County, NJ., family." Also from Stillwell, Vol 5., p. 236, "In 1688 he received from the Proprieters of East Jersey land which was probably th etwo hundred and forty acres of land he held in Middletown in 1688."
So, whereas both Austin and Stillwell assert that Thomas had a son named Gershom, only Stillwell, of these two, asserts that he was the founder of the Monmouth, NJ., family.