Frances, thank you for this. I didn't know about the second marriage of a Robert Gelling and Jane Kelly and as a result I had a muddle. Now it makes sense. This is how I now think they fit.

Robert Gelling (b 1744 s of John Gelling and Catharine Killey of Ballamilaghyn) married Jane Kelly 22 Sep 1770 Braddan:
Their children, all bp Marown:
1. John 25 Aug 1771. Alive 1812, but haven't determined which John he is yet.
2. Jane 30 Apr 1775; bd 4 Feb 1828. Married Robert COTTIER ca 1798. 7 children
3. Esther 28 Mar 1777. Married Charles FAYLE 15 Oct 1808 Braddan. Children Robert & Charles
4. Robert 31 Mar 1779 - 5 Sep 1835. Haven't sorted him out yet.
5. Catharine 18 Mar 1781. Married John KISSACK 9 Jul 1808 Braddan. Children Catherine and William (he married Ann Quine). She later married Charles KEWIN.
6 Thomas 15 Jan 1786. Deceased before 1812 as he's not mentioned in John G's will.
7. Eleanor 9 Sep 1787 (d 1877?) Married Thomas CLAGUE 11 Feb 1804 Braddan 10 children.

Robert Gelling (b 1753 s of John Gelling and Ann Fayle of Ballig) married Jane Kelly 12 Dec 1780 Marown. He was a Schoolteacher 40 years. I think these are their children, all bp Marown:
1. Thomas 7 Oct 1781 - 5 Jul 1849 Stonemason. Wife Margaret, possibly Margaret CREER. At least 3 children, possibly more.
2. Robert 12 Mar 1783
3. John 10 Apr 1785
4. Margaret 4 Nov 1787
5. James 18 Oct 1789
6. William 27 Oct 1793
7. Charles 5 Dec 1795 to abt 1845. M Catharine KELLY 6 Aug 1825 Braddan. Children Catharine and John.

James and William likely died early. They could belong to the first couple, but seem to fit well with the second. All the others have logic. Thomas b 1841 matches the MI for #2, which means the later Thomas must belong to #1.

I welcome any feedback.