Not sure if you're interested in this, but from the Belfast street directories for Cape Street, courtesy of the lennonwylie website:
1918: 22. Boyle, Robt., brick layer
1924: 22 Boyle, Robt., bricklayer
1932: 22. Boyle, Robt., brick layer
Also, your Great Gran's sister Mary Boyle married a Thomas O'Hara in 1904, one of the witnesses was a Margaret Boyle.