He was born the son of MP John Blakeney and his wife Grace Persse of Roxborough House, County Galway, and was a brother of Robert, John and William Blakeney.
He saw service with the British army at Quebec and Staten Island in 1761 while Captain in the Royal Sussex Regiment.
In 1763 and again in 1776, he was appointed High Sheriff of County Galway.
He married in 1782 to Margaret Stafford of Gillstown, County Roscommon.
Their daughter Bridget married Sir Richard St George, 2nd Baronet, and had several children.