Source 1. In Search Of The Passangers Of The Mary & John. Vol. 4. !William Gillett became Rector of Church of England in Chaffcombe, Somerset, England on 4 Feb 1609/10

Source 2. Will of William Gillett made 1641 & proved in the Archdeaconry Court at Taunton 16 April 1641.
An abstract of the will is recorded in New York Historical & Biological Records Vol.. 41: pp 282.83, 1910:

The testator mentioned his sons William, Thomas, Nathan & Jeremiah, his daughters Habiah (Abiah), & Mary, & his brother Richard. He said to all my children in England I give two silver spoones apiece, and this phrase probably meant that he had other children, unmentioned, who were not in England in 1641, and to whom he had presumably given their portions when they left home. Concerning his son Nathan, he said the land which my son William, the next reversioner of said land, shall surrender his estate (therein, etc.he had a bother, Richard Gylett & a kinsman,
Henry Hutchins, maybe a brother-in-law; After his bequests, his will states, The rest of my goods I give to my son, William, whom I make my executor.
(The will mentions Nathan but not Jonathan. It has been established that Jonathan drew on his legacy to make the trip to the New World and was indeed a brother to Nathan.)

Source 3. Will of fahter Richard Gillette of Caudle, Haddon, Dorset, England, husbandman, dated 1 July 1600 which mentions sons William & Richard.
William may have been born in Caudle, Haddon, Dorset, England where his father died. Some of his children may have been born there also;