Do you have a marriage and or death cert for your grand father ?
An English death cert should give reported age (or date of birth on later certs) and a marriage cert should show his father's name and occupation to help confirm the connection back to his parents..
I''ve searched directories up to the 1940s, and no Stewart bootmakers/leather workers listed as businesses on Lower Clanbrassil St., but a couple of places on the street they could have been employed.
e.g. in 1938 a H. Atkin, bootmaker at 87, and an R. Spottiswoode harness maker and 109, and S. Milton & B. Corcoran boot repairers at 113.
On the 1939 voters list there are a number of Stewarts listed at Lwr. Clanbrassil, looks like they are living at no. 16, the same address mentioned on the 1911 census by ColCaff in the reply above
Anthony & Elizabeth Stewart
John Stewart
William & Anne Stewart
Numbers 14 to 17 are listed as tenements, which could account for the separate listings at no. 16 on the voters list. Also listed is a Joseph Stewart at No. 110, which appears to be next door to that harness maker I mentioned