1861 census Onchan
Hugh McCarthy, H. M. 50
Mary McCarthy, W. M. 45
Daniel McCarthy, 14
Catherine McCarthy, mother 76

I copied this down years ago & didn't get all details.

1871 census Manx Arms Hotel, Onchan
Hugh McCarthy, H.M. 60 Innkeeper, Ir.
Mary McCarthy, wife, 55? Ir.
Alicia Hoy, aunt, widow, 72, annuitant, Ir
Henry McCluskey, nephew,unm. 17,apprentice tailor, born Douglas I.O.M.

1871 census: 1 Old Post Office Lane (a couple of doors away from Owen & his children, No. 3)
Patrick McCluskey H. M. 18, fruit dealer, Ir.
Fanny McCluskey, wife, M. 18 fruit d's wife, Ir.

I also came across an examination schedule for St. Mary's School 1869:
John McCluskey aged about 7/8 yrs in Standard 1. Sounds like your grandfather doesn't it?

The monumental Inscription on grave may give more help about Bridget's relationship to Owen. I'll check next time I'm in Family History Room in Peel. Marie