I just checked an old list I created years ago of Gelling burials in Onchan. The 1820 burial is "Wm Gelling (B:Millaghan) age 25 years Jul 3. Soon after in 1823 is "Thomas Gelling (Ballamillaghyn) aged 25 yrs Jan 19 1823". Then in 1825 is "John Gelling (Ballamillaghyn) aged 37 years May 30 1825". Then in 1827 is "Edward Gelling (Ballamillaghyn) 37 Jun 25. Then in 1829 "John Gelling (Ballamillaghan) aged 89 Jul 31, 1829 and back in 1822 "Margt Gelling als Quilliam (Ballamillaghyn) May 11 1822".

The younger ones are all children of John GELLING & Elizabeth OATES, and the latter two are John Gelling's parents. My notes stop at 1849, so I don't have John & Elizabeth who died later.

That eliminates this couple as the parents of William because this particular William Gelling died in 1820. It still leaves the other two to check out.