Hebblewhite was born in Hobart to John Hebblewhite and Adriane (nee Elbrecht). His mother Adriane was a medical doctor who worked for a number of years with the Huon Valley Health Centre until her 2013 death.[1] Kaspar Hebblewhite was educated at the Friends' School in Hobart where he was introduced to rowing. He rowed in that school's first VIII in 2001 with his future Australian lightweight crew-mate Sam Waley. Following school Hebblewhite's senior club rowing was from the Lindisfarne Rowing Club. In 2002 he held a scholarship with the Tasmanian Institute of Sport.[2]
He made state selection for Tasmania in the bow seat of the 2001 youth eight contesting the Noel Wilkinson Trophy at the Interstate Regatta within the Australian Rowing Championships.[3] He rowed in three consecutive Tasmanian youth eights from 2001 to 2003.[4] His brother Ben coxed those 2001 and 2002 Tasmanian youth eights.[5]