Complex sentence: He was a known Catholic, and was married in 1589 to the infamous Lettice Knollys, Countess of Essex and Leicester; she was a daughter of Queen Elizabeth I's cousin and some 25 years his senior.
Split into simpler sentences: He was a known Catholic, and was married in 1589 to the infamous Lettice Knollys, Countess of Essex and Leicester. She was a daughter of Queen Elizabeth I's cousin and some 25 years his senior.