Hey there!
Have no info to provide that would help you in your search, but I am also on the hunt for a Robert Kelso and sometimes it helps to just put it all out there.
Robert Kelso c1800 had a son, Edward c1826. Edward had a half-sister named Esther (Hessy) Kelso who had a child baptized 1843, so she was presumably older than Edward. Unless there was a Kelso=Kelso marriage or an adoption, I am assuming they shared a father until I learn otherwise.
Edward Kelso m Matilda McComb of Larne, Antrim, in 1852, and his father is listed as Robert, occupation gentleman. The couple had at least one child, John Kirk Kelso c1856, though unsure whether he was born Antrim Town or Donaghadee, Down. John Kirk Kelso eventually emigrated to Ballarat, Australia, where he married Elizabeth Carman and had at least one daughter, Lillian Kirk Kelso.
Edward left shares in his will to the 2nd Presbyterian and the Primitive Wesleyan Methodist Congregations in Antrim Town. Why both?
Edward's half-sister Hessy (Esther) Kelso appears to have married a Catholic, Daniel Sheils. No record found as yet. They had at least three children, all bapd St Patrick's RC Belfast: John Charles 1843, Elisa 1844, and Anne 1847.
Edward's will says "late of Donaghadee," when his will was drawn up in 1857, but his executors were residents of Antrim Town. He died in 1859, so sad - his son was about three years old! My thinking is he knew he was ill and relocated for his health - but that is just a theory.
Hessy Sheils (Hester Shields) lived in Ballynafeigh, County Down, now part of South Belfast, in 1862 and moved to Birkenhead, Cheshire, England c1873 with her daughter Elizabeth (Rice), and where she died in 1892.
No idea if Anne Sheals b1847 survived. John Charles Sheils lived, procreated, and died in Ballynafeigh (Down, Ormeau on census).
Derry hadn't even been considered as the origin of Robert until I saw Tamlaght O'Crilly on a map and realized its proximity to County Antrim, and could possibly answer why Edward set up shop in Antrim Town or how he even met a girl from Larne.
No siblings mentioned in Edward's will other than Hessy. If Edward's marriage record is correct, he was born 1826, so I would imagine his parents' marriage would have taken place not long before then.
What struck me as unusual was the emigration of so many Kelsoes from Derry to Australia, and I was wondering if John Kirk Kelso may have known another Kelso who was already there before emigrating.
Also curious is his name, JOHN KIRK Kelso, and his daughter LILLIAN KIRK Kelso. Who were these Kirk people? There is a John Kirk, Loan Fund Manager, in Antrim Town in 1852 street directory, but I have yet to connect the name Kirk with Kelso as yet.
Any help to further my search would be greatly appreciated.
