Many thanks Aghadowey for your quick response, much appreciated.
Margaret and Gaetano 's children were all born in Indiana, US. Word from them and the Mormon Index is that Gaetano Ponti was from Milan (b 1843) unfortunately he does not appear on the Ancestry passenger lists. Margaret is said by them to have been from Belfast (there is no actual evidencve of this) and that they married "about 1870 in Belfast".
If this is true then they married just before emigrating.
I am really more interested in Margaret and her family's origin. Her brother Robert Nelson b abt 1845/6 was my g grandfather and certainly married (1865) and lived in Liverpool, possibly emigrating in 1868 to US, he (or someone very like him) appears in the 1868 passenger lists.
Robert Nelson was a stonemason, are there are N Ireland trade directories that might show him or his father James who was a painter around this period?
regards