James Fay b 27 Dec 1707 m 9 Dec 1727 Lydia Child, dauof Joseph and Sarah Child of Watertown, MA. He is the son of John Fay (II) and Elizabeth Wellington.(James/JohnII/JohnI)
His wife, Lydia Child, should not be confused with a Lydia Child born in Springfield, MA. Joseph Child and wife Sarah of Watertown should not be confused with Joseph Child and wife Ruthor a Hannah (see below). The Child family is an extensive genealogy as is the Fay's and the confusion relating to Fay genealogy appears to relate to brothers and cousins in marriage with common names shared each generation.
Consider the migration of ancestors i.e. James Fay origin can be found in Westboro, MA - a region where various sons from John Fay established Marlborough, Eastboro, etc. He migrated from Westboro to Grafton, settled 1746 in Hardwick, MA where he died 12 June 1777. Migration helps narrow the gap of possibilities throughout Massachusetts. This was the era of founding families and new towns.
I have a bio on James Fay if you are interested.
My ancestry: Stephen/JohnII/John I. Stephen Fay b1715 married Ruth Child, daughter of John and Hannah Child. Confusion arose early in research because John and Hannah had a daughter named Lydia I believe. Stephen was in Westboro with his older brother, James, and migrated to Hardwick in 1746 together. Your James was a leader in the church and my Stephen was a leader of the "state". Stephen removed to Bennington VT around 1760 along with other Fays to founded the Republic of Vermont (1790) along with other Fays and Ethan Allen and his Green Mountain Boys.
Take a look at the Child family genealogy of Watertown and you will find family relationships between John Child and Joseph Child as we find between your James and my Stephen. There is also a close family relationship between your Lydia and my Ruth Child. I don't have the Child genealogy with me to share particulars.