John Killey and Ann Cubbon married 1834 Patrick 2 children: Joseph chr. 1835 German
Ann chr. 1839 German & buried 1840 Patrick (9 mos)

1841 census
Knockaloe beg
lists John Killey, his 2nd wife Ann and son Joseph age 5
also Curtis Sittin age 4
On the 1851 census Curtis Sittin becomes Curtis Seddon age 15 a lodger living with another family. I think there was a Sittin or Seddon family living in the parish at that time.

Children of Margaret Killey and Hugh Kneale
are:
Margaret chr. 1822 Braddan
Elizabeth chr. 1825 Braddan
Ellen chr. 1828 Braddan
John chr. 1833 Onchan parents Hugh Kneale and Margaret

If Hugh Kneale is living in 1851 then the Margaret you are looking for is not Margaret Killey chr. 1801 parents John Killey and Isabella Quayle.