Complex sentence: He married his first wife, Mary, who already had a two-year-old daughter, when he was in his early twenties; they had two daughters together and divorced 13 years later in 1971.
Split into simpler sentences: He married his first wife, Mary, who already had a two-year-old daughter, when he was in his early twenties. They raised two daughters together and divorced 13 years later in 1971.