Compare:
[#6705506] My brother who lives in Boston is a carpenter. (CK) *audio*
[#6705507] My brother, who lives in Boston, is a carpenter. (CK) *audio*
Compare:
[#6705506] My brother who lives in Boston is a carpenter. (CK) *audio*
[#6705507] My brother, who lives in Boston, is a carpenter. (CK) *audio*