Below is the inscription from the headstone of Jeremiah and Isabella McIvor family in Mullinahoe graveyard, Ardboe. Although I had photographed and transcribed all the headstones in this graveyard several years ago, I went back today and re-checked this one because Jeremiah's apparent age gives him a year of birth approximately 1837. I re-photographed the inscription just to be doubly certain - it has been cleaned since I first photographed it.
My assumption would be that this Jeremiah (d.1900) was a son of Jeremiah McIvor and Anne McSloy, was a brother of Mary (b.1832) and of John (b.1836). I wouldn’t be overly concerned by the fact that there is no entry in the baptismal records: this is a not uncommon occurrence, for instance my own great grandfather was baptised in Ardboe in 1839 but he does not appear in the register. I know from perusing the registers that they were only written up every few months, and inevitably some slips of paper with baptismal details on them had been lost before the official entry could be made.
It is feasible that the Jeremiah who married Anne McSloy was also the Jeremiah who married Sarah McIvor in 1849.
Pray for the souls of Jeremiah McIvor, Ballymurphy, died 6th May 1900 aged 63. His wife, Isabella died 7th April 1910 aged 67. His daughter Annie died 8th March 1909 aged 23. And his sons, James died 27th April 1933, aged 54. Jeremiah, died in U.S.A., April 1945. His daughter in law Mary McIvor died 1st Oct. 1956, aged 57. And her husband John McIvor died 5th Feb. 1983 aged 97. Hugh died in Glasgow April 1965 aged 76. R.I.P. McIvor
Perhaps you will let me know what you think as regards this.