Source: Michael Doyle Their Name Liveth For Evermore: The Great War Roll of Honour for Leicestershire and Rutland.
He was the son of Thomas Clarke a shoe trade finisher, born 1861 in Sileby, Leics., and his wife Isabella a seamstress, born 1859 in Kilrea, County Derry, Ireland. Sidney was born in 1898 in Sileby, Leics., his siblings were, Georgina, born 1895 and Norah, born 1897, both his siblings were born in Sileby, Leics., his half blood siblings were, Alfred, born 1881, Mary H., born 1886 and Eliza Ann, born 1888, all his half blood siblings were born in Sileby, Leics., his step siblings were, Thomas Underwood, born 1887 in Natal, South Africa and Isabella, born 1891 in Sileby, Leics., in March 1901 the family home was at Swan Street, Sileby, Leics. In April 1911 Sidney was a scholar and was residing in the family home at Swan Street, Sileby, Leics., together with his parents and siblings, Georgina and Nora, his half blood sibling, Eliza and his step siblings Thomas Underwood and Isabella Underwood.