Hello!
Isabella's 1958 death certificate (attached) is signed by her son "G McIntosh" of 582 Brethour Avenue in Sidney. In the 1955 Sidney directory, the last one available online, he is listed "George G McIntosh" of 582 Brethour Avenue. I lived on Brethour Avenue a few years ago but it's a much shorter road now so 582 no longer exists. Anyway, he was definitely George.
So far I've not been able to find any death record for George but the BC Archives only goes to 1991. I'll try and search for obituaries and other information about the family and will post again if I find anything.
It appears all the family was buried at Royal Oak Cemetery so you could contact them to see if George is also buried there. Here's the email of the person at Royal Oak who deals with grave locations and other information:
susan.mcmullen@robp.caI'm also attaching his dad's and sister's death records in case you don't have them.
Cheers,
Soosi