On birth the nearest nearest information from more reliable sources is a child born in the correct year in Milton between Dumbarton and Old Kilpatrick, the son of a Dumbarton-born Mary McGarry, a Paper Mill Worker, and Mark Ponsonby, a Rivetter, also from and living in Dumbarton. At birth the wean is registered illegitimate but it seems the couple marry actually in Dumbarton once more but a month later. Moreover, with regard to the Northern Ireland connection the father then seems to have moved to Belfast. His death is recorded there in 1889. But the mother seems to have remained in or perhaps returned to Scotland dying in Greenock in 1907, whilst her son's death is reported not as 1962 but 1952 (however at the age of 77 so born in 1874) and also in Glasgow, but in the Western Infirmary to be precise so perhaps living elsewhere. And to add grist to the mill firstly a Mary and a John Ponsonby are recorded in Dumbarton again staying with family in 1881 and a Mary Ponsonby is in 1891 living with her McGarry sister in Bonhill, Dunbartonshire and working in the print-fields, which leaves open the possibility that young John might have leaned his football at The Rock or even in the Vale of Leven, and secondly in 1901 a Mary is staying Greenock and acting as housekeeper to her McCarrie cum McGarry elder brother. 

Thus a more correct story of Jack Ponsonby may be as follows with the mystery still in reality unresolved, at least not fully. 

"He was born in 1974 in Old Kilpatrick in Scotland, went with his parents to Northern Ireland and remained there after the death in 1889 of his father, his mother returning. To support this the 1901 Irish census shows a 25 year-old, single, Scots-born John Ponsonby, shipyard rivetter, so having perhaps followed his father's trade, boarding in Belfast and in 1902 there is again a Boilermakers' Union card again in Belfast in the same name and now aged 27. (But there are in both cases two problems. He is a couple of years too young and his birthplace is given as Glasgow, not Dunbartonshire.) 

Then sometime after 1904, perhaps even on his mother's death, probably pre-Great War but maybe post-, a John Ponsonby seems to have returned to Britain generally and then Scotland specifically. In 1908 there is again a Boilermakers' card, this time for a thirty-two year old now in Middlesbrough. Moreover by 1921 there is a 46 year-old John Ponsonby born in Milton living with his wife, Maria, childless, in Old Kilpatrick, when ten years earlier there was no-one of his name of the right age and for the previous fifteen years no recorded marriage of the couple in all Scotland or England (which does not rule out Ireland). And this John Ponsonby was indeed to die in 1952 in a Glasgow hospital but with no known place of burial and therefore completely unrecognised, to which can now be added the following. His wife was Maria Isabell Lett, born near Keswick, her birth was in 1864, so she was a decade older than he and she pre-deceased him, dying in 1946 and also in Glasgow."  

All of which means that although John Ponsonby was by most accounts a Scots-born international footballer for Ireland he is the only one, whose fate is nebulous and despite being part of the Irish Trail is the only one neither born nor buried anywhere on The Emerald Isle.