JOHN FERRIE was born Abt. 1857 in Donegal. He married Margaret Porter on the 28 Apr 1904 aged 24 in BURT Co. Donegal, daughter of JOHN PORTER and Ann McIntyre makes more sense......
Margaret daughter of JOHN PORTER and ELIZABETH MULLEN. according to the 1901 and 1911 census gives her birth as 1889 which does make her 14? The 1911 census says she 22 and unmarried..... so your Margaret obviously is not daughter of JOHN PORTER and ELIZABETH MULLEN!!