It is possible your ancestor belonged to an old family from the Douglas area.

The family of Caralagh had its surname translated to Careful.

James son of Richard Caralagh and Jane Key bap Braddan 22 Oct 1780. Seems a bit late for a 1798 marriage, but the I.G.I. struggles with the surname & it would pay off to check the microfilm of the Braddan& Douglas registers for other baptisms.

Richard was buried at Braddan as "Richard Careful" aged 91 on 3 Oct 1817.

Jane Careful alias Kaye Bur Braddan 21 Nov 1831 aged 93,

Careful is the same name as Caralagh & Kaye is the same as Key!

Happy hunting