Early Life
John Shayle was born around 1580 (based on extrapolation from the dates of birth of his children). I haven't found any baptismal records for him yet; there's a record on FindMyPast of a John S. who married Margerie Gardiner in Painswick, Gloucestershire, in 1605. This looks a bit too far away from Dymock to be the right person. Ancestry has a John Shaile baptised in 1580 in Dymock, son of Richard Shayle. However the underlying document is incredibly hard to make out.
British History Online has an entry for Dymock, which mentions the Shayle family many times. There is mention of a John Shayle who died in 1685, who might be this John Shayle. It looks like that John was son of Thomas, son of Thomas and Elizabeth.
In the
Visitations of Gloucestershire1, he is referred to as "John Shale of Dimock, co. Glouc, Gent".
Footnotes
[1]
Visitation of the County of Gloucester, 1682-1683, ed. T Fitz-Roy Fenwick and Walter C. Metcalfe, Exeter, 1884; Cox, alias Hayward of Woolstrop in Quedgley and Forthampton, pages 49-51