It might be best to start from the 'beginning' with known facts to get more family information.
To start with, IGI (
www.familysearch.org) lists 3 sons of Robert McMaster and Mary Elizabeth Eccles which points to an area outside Ballymena town.
1. James McMaster born 8 Jan.1865 Glenwhirry, Co.Antrim (page 157 in civil register)
2. Samuel McMaster born 4 Feb.1867 Glenwhirry, Co.Antrim (page 157 in civil register).
3. John McMaster born 29 Nov.1869 Co.Armagh (Armagh could be a mistake if wrong item was selected from drop-down menu when inputting record into IGI database).
There is an 1852 marriage in Co. Antrim for a Robert McMaster to a Mary Elizabeth ? . If this is the correct marriage there were likely several children born between 1852 (marriage)-1864 (astart of birth registration).