Sidney Crowther was born in the early part of 1875 in Keston, Kent and grew up at Holly Lodge. He was the son of Alfred H. Crowther, a solicitor, of Gray's Inn and Mary Crowther. He had a number of siblings, including Julia (b. c1866); Nelson (b. c 1872); Keston (b. c. 1874); and Bertrand (b. c 1877). Sidney attended Warwick School, and was the first Old Warwickian to gain international honours for Great Britain, when he later went on a tour to Australia and New Zealand. In the same school rugby side as Sidney was Robert Challoner who emigrated to Australia and represented New South Wales and later Australia in the second test against a touring Great Britain side in 1899.