Sir Henry was the son of Henry Maynard, Rector of Radwinter and Vicar of Thaxted, in Essex, and his wife, Susan. The younger Henry succeeded his uncle Charles, 5th Bt. and 2nd Viscount Maynard, who died without children on 10 March 1824. (The Viscountcy had devolved upon Charles from a somewhat distant relative.) He served as a lord-lieutenant and vice-admiral of Essex. On 28 December 1810, he married Mary [d. 1857], daughter of Reginald Rabett, Esq. of Bramfield Hall, Suffolk. They had a son, Charles-Henry, and three daughters: Charlotte-Mary, Emma, Catherine, and Julia.
Burke, Sir Bernard. A Genealogical and Heraldic History of the Peerage of the British Empire. 26th ed. London, 1864: 750-51.