Only son or only surviving son.
If 1844 and if Vol 1 then only one.
HARRISON, THOMAS - HAMMOND
GRO Reference: 1844 J Quarter in SAINT PANCRAS Volume 01 Page 288
HARRISON, THOMAS - HALL
GRO Reference: 1844 M Quarter in FARNHAM Volume 04 Page 129
HARRISON, THOMAS - GOURD
GRO Reference: 1844 J Quarter in ROTHERHITHE Volume 04 Page 398
HARRISON, THOMAS - SANGSTER
GRO Reference: 1843 M Quarter in MARYLEBONE Volume 01 Page 253
HARRISON, THOMAS - ROYAL
GRO Reference: 1845 D Quarter in SAINT GEORGE HANOVER SQUARE Volume 01 Page 25