In the 1861 census I find:

RG9/4412, Braddan, District 5, Folio 85, Page 12, Schedule 48
Ballamoda Road, 5th house
Matthias Cain, Head, 53, Blacksmith, Marown
Margaret Cain, Wife, 50, his wife, Braddan

They look like your people but just in case there is also:

RG9/4416, Braddan/Douglas, District 1b,
Folio 36, Page 25, Schedule 278
South Quay
Matthias Cain Jr, Head, 24, Joiner
Margaret Cain, Wife, 25
(next door = Schedule 279)
Matthias Cain Snr, Head, 68, Joiner, Braddan
Jane Cain, Wife, 65, Oncahn
Elizabeth Watson, Servant, Unmarried, 16, House servant, Rushen
Agnes Halsall, Neice, 5, German

I couldn't find Luke in 1861, assume Rebecca and Sophia had married by then and would need a year of birth for William to locate him.

Cheers,
Ruth
Canberra - Australia