This looks like another son of theirs:
John Robert Illegitimate son of J Quayle & Elizabeth Kneale bapt Parish Church 30 Mar 1843.
They married in Maughold on 20 Dec 1845.

The 1851 Maughold census, Ballacannell, has John Quayle Hd, mar., aged 31, Agricultural labourer, b.Lezayre, with wife Elizabeth ag.33 b.Maughold, and children Eleanor 9, John 8, Ann 4, Thomas 1, and Catharine 1m, all b. Maughold.

Sue