Complex sentence: Educated at Reading School and at Winchester College, Henry Vansittart joined the society of the Franciscans, or the "Hellfire Club", at Medmenham, his elder brothers, Arthur and Robert, being also members of this fraternity.
Split into simpler sentences: Educated at Reading School and at Winchester College, Henry Vansittart joined the society of the Franciscans, or the "Hellfire Club", at Medmenham. His elder brothers, Arthur and Robert, were also members of this fraternity.