Hmmm. Isaac Kingwell isn't a very common name. I had a look and can't find another one that fits.
I traced this George a bit further. He's still unmarried in 1901 but the 1911 census index (
www.1911census.co.uk) seems to show him (the full details are pay per view) in the Plympton district with father Isaac, wife Evelyn and children Arthur age 6, Percy age 4 and Stanley age 2. FreeBMD shows that Percy's full name was Percy Reginald. George Samuel Kingwell married Evelyn Kennard in 1904.
I wrote this earlier, so just so I don't have to do it again if it turns out to be the right family after all.
If you want to search for Isaac's marriage then you can go to
www.freebmd.org.uk . When you find him, click on the page number to see who were the possible brides. You'll see 2 female names - knowing her first name (1881 shows that she's Ann H), there will be only one possible.
Then go to
www.familysearch.org and find Issac's christening. (You should see 3 records - make sure you only trust the one that says 'Extracted birth or christening record for the locality listed in the record')