I can find no record for either George Isles nor his brother Joseph. There is, however a entry in the 1901 census ...
North Side, North Street, Cargill, Perthshire
David Isles, head, 37, railway surfaceman, b. Cargill
Mary Ann Isles, wife, 37, b. Errol, Perthshire
Andrew Isles, son, 11, scholar, b. Cargill
Margaret Isles, daughter, 10, scholar, b. Cargill
Joseph Isles, son, 8, scholar, b. Cargill
Charles isles, son, 6, scholar, b. Cargill
James Isles, son, 3, b. Cargill
George Isles, son, 1, b. Coupar Angus, Perthshire
There is an entry on the CWGC site for a J Isles of the 11th Bn., Border Regiment. He is down as the son of Mr. & Mrs. David Isles of Scott Street, Burrleton, Perthshire. This is not very far from Cargill.