They were not very good about baptising all their children! (Or I'm not very good at finding them.)
1841 census Ancestry index [with my additions/corrections from the scan]:
Name: Charles Lewin
Age: 35
Estimated Birth Year: abt 1806
Gender: Male
Where born: Isle of Man, Isle of Man
Civil parish: Braddan
County/Island: Isle of Man
At Braddan, Baldwin [all b.Isle of Man]:
Charles Lewin 35 Ag Lab.
Isaballa Lewin 32
James Lewin 12
Elizabeth Lewin 10
Margaret Lewin 8
Richard Lewin 5
Robert Lewin 3
Ellen Lewin 1

IGI has ELEANOR LEWIN Christening: 27 MAR 1840, Saint Lukes, Baldwin, Isle Of Man Father: CHARLES LEWIN, Mother: ISABELLA CAINE.

Also in Baldwin in 1841, on the same page as Charles & Isaballa Lewin, were Matthias Cain 35 Blacksmith, Margaret 30, and William 10, Sophyah 9 and Rebecca 2, followed by John Cain 24 Tailor & Margaret 22.

The 1851 & 1861 transcripts are at the very end of this thread:
www.isle-of-man.com/genealogy/messageboard/index.pl?page=1;md=read;id=543820

- Showing youngest son Jacob who was the uncle with whom James & William Starkey lived after 1871. The 1871 census showed the children with Charles & Isabella Lewin:
www.isle-of-man.com/genealogy/messageboard/index.pl?page=1;md=read;id=543783

I couldn't find James Starkey & Margaret Lewin which is why I was hoping for a MI or burial in Braddan/Douglas or Malew to show they had died.

All the children of Charles Lewin & Isabella Cain (found) bapts were at St Lukes, Baldwin, except for Elizabeth who was bapt 13 NOV 1831 Braddan [IGI].

Sue