Splatt was born at Northwood Farm in the parish of Chudleigh, Devon, England, the eldest son of John Splatt (born 1780), a yeoman farmer born in Kenton, himself the son of William Splatt of Kenton, by his wife Anne.
He was educated at the well-regarded Kentisbeare School, and later worked at Chudleigh as a solicitor's clerk for Charles Langley.