Complex sentence: On 27 February 1654, Strafford married Lady Henriette Mary Stanley, the daughter of James Stanley, 7th Earl of Derby and Charlotte de la Tremoüille, Countess of Derby.
Split into simpler sentences: On 27 February 1654, Strafford married Lady Henriette Mary Stanley. She was a daughter of James Stanley, 7th Earl of Derby and Charlotte de la Tremoüille, Countess of Derby.