Have you tried taking a look at the NB archives online?
I found the marriage there for John and Margaret1863 - which shows Alexander Gibson as so-signer,
and what looks like it is John'sdeath in 1910. He is also listed under Cemetery entries showing death as in 1910 and being husband of Margaret K. Blair. He is buried in United church of Canada, York County cemetery
it says Margaret K. Blair has same stone as husband and shows her death as 1910 also
There are also some births of children:
delayed birth for Margaret Eleanor Blair, born Jan. 7, 1877, daughter of John Russell Blair and Margaret King Gibson. There is an image for this record.
birth of son John Frederick Nov. 25, 1872 -delayed birth record with image
there are also several records for grandchildren of John and Margaret. If you just go to the Federated Database search and enter the Blair name(entering any you know of for sure) and see what comes up.