The birth posted for Samuel George Boyd is your grandfather's. Have another look at the image and keep in mind that
1) the informant was a neighbour (midwife?) Sarah McDowell and she likely muddled up Mary's maiden name
2) the place of birth was 11 Donegore Street. A few months before, in July 1895, your Boyds were living at 19 Donegore Street when second Samuel died.
I'm wondering if Samuel George Boyd used a baptism date if he couldn't get a birth certificate. If he applied for his birth certificate saying mother was Mary Brown he could have been told the birth wasn't registered.
Not sure if this is Samuel George Boyd or his father-
Northern Whig, 26 June 1924: Beasts of Burden… best decorated donkey and cart- 1. Samuel Boyd, 118, Urney St.
children of Samuel & Jessie?
Mary born 4 Dec.1921, Robert born 16 Jan.1923 (both in Belfast, father- Boyd mother- McCullough)
Will save Mary/Minnie (Boyd) McClurg for next post.