Not sure if you have this already-
Belfast Newsletter, 11 Jan.1877- Marriage- ALLEN-LEIGHTON- January 10, at St. Anne's Church, Belfast, by the Rev. Dr. Hannay, David Allen, Lisburn, to Martha, fourth daughter of Mr. Richard Leighton, Belfast.
Puts David still in Lisburn 1877 and gives a name for Martha's father in Belfast.
Which leads us to Richard Leighton- "The Will of Richard Leighton late of Bow-street Lisburn County Antrim Book-keeper who died 4 March 1890 at same place was proved at Belfast by Samuel Leighton of 6 Cooke-terrace Ormeau-road Belfast Artist the sole Executor." Will mentions son Samuel, 3 grand-daughters (including Mabel K. Allen).