Thanks Frances. I have actually got your cd (well, 2 since April!) and had found

Braddan Marriages 1771-1800
3 Apr 1796 WILLIAMS Francis, Serjeant 2nd Corps RMF, & COWLEY Esther, otp ipo Wm Shimmin; tc [Thomas Curphey] [Manx Notebook]

but was worried about going too far as I only had IGI entries to go on:

Maria Kenyon d/o Henry Kenyon & Esther Cowley c. 9 Apr 1815 Ballaugh IGI ext

Henry Kenyon married Esther Mrs Williams 12 Dec 1811 Braddan IGI ext.

I couldn't find a burial for Francis Williams or Esther Kenyon [Henry seems to have been buried in 1837].

I thought the Esther d/o William Cowley & Isabel Craine c.12 Aug 1772 St Matthews IGI ext looked likely too, as this would make her 39 when she married Henry Kenyon, which could account for her having only 1 child (so far as I know anyway). E. d/o William Cowley & Esther Clague (an initial favourite with wills and everything) would have been too old with a 1759 baptism in Braddan.

Still can't see where Kewley comes in though.