Perhaps there is an error with the marriage record? From SP:
ALEXANDER Graham married GORMILIA 1857 Barvas (not opened record to see surname)
1881 Census - 13 Back
Alexander Graham 50, a fisherman. CORMELIA Graham 45, wife
Catherine Graham 14, 3 other siblings
1891 Barvas
Alexander Graham 58 Crofter, GORNULIA Graham, wife
1901 8 Back
Alexander Graham, 70, Crofter and fisherman, GORMILIA Graham, 65, wife
brigau
Added: Sorry, I'm not seeing things - the 1857 marriage was for Alexander Graham and Gormilia MURRAY