Hello,
         I have looked at the Thomas Glass + Mary Jane McElroy pairing as I believe , but cannot prove , that Thomas was a younger brother of my Great Grandfather , Samuel Glass. Samuel Glass + Margaret Rae ( Wray) were married in Clogherney parish as were Thomas + Mary Jane, as you know.
         This is such a small place, that it seems likely.
         I believe Thomas + Mary Jane had these children that I can find so far :-
       William James Glass b 29 Aug 1866 , Six Mile Cross, Co. Tyrone
       Margaret Glass           14 July 1868                          Co Tyrone
       James Glass                28 Dec 1869                           '
                                            a possible marriage - Mary Anne Graham  16 - 11 1893 , Clogherney Parish
        Samuel Glass             28 June 1871   Six Mile Cross         "
        John Glass                 23 Mar   1874                          Co Tyrone
        These childrens names match the family names of the children of Samuel Glass + Margaret Rae.
         Samuel Glass` father was Samuel and Mary Jane`s father was James McElrae.
        Don`t know if any of that is helpful but it is what I have gleaned so far,                                       Regards, Thommoje