"I believe he was my grandfather's {Robert] brother, sons of a John Cunningham from the Belfast area. My grandfather left for South Africa in 1901 and seems to have lost all contact with the 'Antrim' family..."
How old was your grandfather in 1901?
The Lowry Cunningham who died in 1877 aged 48 would have been 71 by then and unless an elder brother by many years this would be quite old to travel surely?
The Lowry Cunningham on the 1901 census
LINK that Maggsie found is aged 40 which may be the correct age to be your grandfather's brother but too young to be the man married in 1864
However, there is a further baptism for a Rachel Cunningham in Tipperary; May 29 1873
Father Lowry, Station Master; Mother shown as Maria Stroker which I now think is a mis-transcription
It is possible that the Lowry on the 1901 census is a son that I haven't located
If Robert, was the son of John, it is more likely that the
Lowry Cunningham that married Jane Grey on Sep 05 1872 in Seapatrick, Co. Down is correct
He is shown as a plasterer, aged over 21, a widower, s/o John, a plasterer
She is shown as a spinster, aged over 21, d/o Alexander
Both of Dromore Street, Banbridge and both Methodist
which ties in with your other post
LINKI don't see a Railway Station Master becoming a plasterer at that time though
