If they met while the regiment was stationed in Glasgow, it's quite possible the marriage and birth of child took place in Ireland after the regiment moved there. The first 6 months in Ireland they were headquartered at Birr, and then moved to Athlone, with maybe the final couple of months at Curragh.
These are the approximate dates of movements of the 59th Foot after leaving South Africa in 1862.
Jan 1862 to Dover
Jun 1863 to Aldershot
Mar 1865 to Glasgow
Jan 1866 to Ireland
Nov 1867 to Ceylon
Jun 1869 to India, where they stayed for many years.
When the 59th Foot arrived in Glasgow, in March 1865, it was in the troop-ship Himalaya. It carried 23 officers, 783 men, 103 soldier’s wives, 102 soldier’s children, 7 horses, and the heavy baggage of the regiment.
Rex