Hi,
Welcome to Rootschat. I have found the marriage and there are at least nine children.
21 Jun 1864 John Allan married Martha Giffin in Cullybackey Reformed Presbyterian Church, Ballymena.
The fathers were Robert Allan and Thomas Giffin. Children were:-
14 May 1865 Robert (died young)
28 Oct 1866 Mary
19 Dec 1868 John
15 Dec 1869 Thomas James
12 Apr 1871 Robert
4 Oct 1872 Jesse Anderson
3 May 1874 Martha
17 Dec 1876 William
26 Jan 1879 Arthur Ross.
Regards