Complex sentence: Two years later in 1845, Gay married Elizabeth Johns Neall, the daughter of Philadelphia's prominent Quaker abolitionist Daniel Neall, who was herself an abolitionist and involved in the woman's rights movement of the day.
Split into simpler sentences: Two years later in 1845, Gay married Elizabeth Johns Neall, the daughter of Philadelphia's prominent Quaker abolitionist Daniel Neall. He was married in 1845 to Elizabeth Neall who was herself an abolitionist and involved in the woman's rights movement of the day.