Hi there,
The IGI shows one birth for a George McNair for 1836 + or - 2 years, for Lanark:
Born 02 May 1835 and Christened on 05 Jun 1835 in Barony parish, Lanark. Parents given are James McNair and Eleanor Stanser. However, I cannot find a John born to these parents.
Looking farther afield than Lanark, there is a George McNair born in 1831 in Argyllshire, but again I can't find a John to match.
Do you have any ideas about their parents' names?
Cheers,
Clare