Actually the McCrea family's connection to the Hanna's is like this:
Margaret Hanna married Robert Scott
their daughter Elnor Scott married John Alexander Hill the son of
John Henry Hill and Margaret McCrea (from County Monaghan) later of Douro Twp, Durham Co., and Pilkington Twp, Wellington Co.
I think all these families - Hanna, Scott, Hill and McCrea had some connection either socially through the church or military membership when in Ireland.