Abstracted from Wiley's Book of Nutfield, Bolton's Scotch Irish Pioneers in Ulster and America, and Perry's Scotch Irish in New England:

There is some question as to whether it may be a second wife of John Stewart, also named Elizabeth, but with a maiden name of Forsythe, that is buried in Colrain,MA. The possiblility is as follows -- John Stewart came to America in 1718 and was one of the proprietors of Londonderry,NH. He came with his wife and several children, his mother, brother Robert, and Robert's two sons. Elizabeth Clark Stewart gave birth to their youngest son Samuel aboard ship in Boston Harbor.

There is no record of Elizabeth Clark Stewart after that point. Then John married Elizabeth Forsythe (parentage unknown) and they had two children Joseph (born 1721) and Margarete (born c1723). It would therefore be Elizabeth Forsythe Stewart who went to Colrain with Jeanette Forsythe Stewart after John's death in 1741.

The records are vague about his first wife as well as the second wife, who might be a cousin as his mother's maiden name is also Forsythe.

John married (1) Elizabeth Clark (daughter of John Clark) and (2) Elizabeth Forsythe, both in Ireland. John moved (from Ireland?) to Boston in 1718 and Londonderry, NH in 1719 (letter from Philip B. Stewart, 6 Sabal Ct., Sewall's Pt., Stuart, Fl., 4/24/1990).
Although born in Scotland he returned to Ireland, where he had spent his early years. At this time the Presbyterians were still subject to discrimination. Also at this time rents on farmland were doubled and tripled, causing great hardship. John belonged to the Presbyterian congregation of Aghadowey, led by the Rev. James McGregor. A group of these, accompanied by McGregor, emigrated to America, landing at Boston on October 14, 1718. In the spring of 1719 sixteen of these families proceeded to New Hampshire, where they founded Londonderry, named after their home county in Ireland.

John's tombstone reads:

Memento Mori

Nam sito labitur hora

Here lyes the intered body of
Mary Stuard, the daughter of
John Stuard and Eliz his wife,
who departed this life November
the 7, 1738 and in the 22
year of her age.

Here lyeth also the body of
John Stuart father of the
aforesaid Mary who departed this
mortal life about the 60 year of
his age and on the 6 day of
April Anno Domini 1741.