I've been looking again at Thomas Gelling who married Agnes Anne Brough:
1841 IOM census (Ancestry Maughold, district 2, page 12 )
Thomas Gelling age 25 miller born IOM
Agnes age 20 born Scotland
Mary age 1 born IOM
William Brough age 9 born England
Another Thomas Gelling of the same age is in Douglas:
1841 Conchan district 9 page 11
Thos Gelling age 25 no occ given Y
Diana Gelling age 21 dressmaker Y
Mgt Regan age 21 dressmaker E
GELLING Thomas 25 Dou 1465/8 13 21
The Diane Gelling has a conveniently unusual name for that era, and she's almost certainly Dinah Gelling, bap 4th June 1820 Braddan to Paul Gelling and Elizabeth Garrett (extracted ). She married John Kelly 20 June 1841 in Liverpool, and is with her husband and children in Liverpool in 1851 (St Martin, district 1k, page 35 ) age 31.
Dinah had an older brother, Thomas bap 17 Nov 1811 Braddan ie Eric's #2.
So can we now safely say that of Eric's 3 possibilities for the parents of Thomas Gelling, husband of Agnes Anne, we've eliminated #2 and #3 ?
"The IGI gives the following for baptisms of Thomas Gelling:
1. 11 Nov 1810 St. George, Douglas, son of John GELLING & Ellinor CRELLIN. They married in 1798 Braddan and I have 4 children: John 1803, Margaret 1805, Thomas 1810, Charlotte Elinor 1816. The first 3 were St. George, and Elinor was Marown. I haven't researched these people, so that's all I know.
2. 17 Nov 1811 Braddan, son of Paul GELLING & Elizabeth GARRETT. They married 2 Jan 1802 Braddean and I have 8 children, all Braddan. I have a note that Paul may be son of Paul Gelling & Jane Gelling of Camlork, but that might be wrong. I know little else.
3. 10 Apr 1812 St Mathews Douglas, son of Thos GELLING and Ann [MOORE]. I have him tentatively as the one marrying Anne Esther BRIDSON in 1846 at Malew with 6 children. However, I'm looking at this now and think this could be the one, and my tentative other family is wrong. Children naming pattern is good (first son is Thomas, first daughter is Mary Ann). "
Which leaves either #1, or a Thomas who isn't in the IGI.