Hugh shows up in 1716/1717 as marrying "Mary Coal" in Lebanon, Connecticut. The same Hugh (of Lebanon) purchases land in Mansfield in 1725. Andrew marries Ruth Stebbins Dexter in Mansfield, Tolland, Connecticut, not Lebanon, New London, Connecticut (which is what you said above), in 1738. That is a big difference -- one that endorses the idea that Andrew is son of Hugh and is born in 1717/1718 (same time as the widow Ruth Stebbins Dexter, whose first husband had died within a month of their marriage prior to 1738).
I am unconvinced of the Galston, Ayrshire proposal because there are no records of voyage and there are children listed here that are born at the time that Hugh of Lebanon and Mansfield (same person by record of land purchase and his first marriage) is documented in Connecticut. I have yet to see any proof that this nice family in Galston came to the Colonies.
Additionally, FamilySearch, the source of the Galston query, and the Parish register identify Andrew as being born in 1710/1711, not 1717. Where do these children appear in Connecticut (or New England in general)? Why does my line of Peter and Horace, related to Andrew & Hugh, appear in places where Voluntown Campbells have moved between 1780 and after 1800?
I propose that Andrew is son of Hugh of Lebanon and Mansfield and is born in 1717/1718, the same age as his wife Ruth, the very young widow that he marries in 1738 that was originally a Stebbins and became a Dexter by her first and short-lived marriage. I also lightly propose that Hugh is born between 1690 and 1700, more likely around 1698, and is a son of one of the Voluntown Campbells. I have read in one or two places some mention of a Hugh Campbell of the Voluntown family. Lebanon is not far from Voluntown.
Here is the documented info I am looking at:http://wc.rootsweb.ancestry.com/cgi-bin/igm.cgi?op=GET&d...
Lebanon VR:1:45 marriage. TAG:51:117. MLR:2:452 (1725) HC of
Lebanon buys 10 on ES Coney Rock Hill. MLR:3:790 (1736) HC
house probably on Wormwood Hill Road. Kline:343 HC L31.10 (1737
2nd Soc tax list 36/62). Klin:354 HC L27.05 (1744 2nd Soc tax
Marriage 1 Mary Coal
Married: 01 MAR 1716/17 in Lebanon
Marriage 2 Abigail Nichols
Married: 18 APR 1728 in M[ansfield]