Complex sentence: Bierce married Mary Ellen "Mollie" Day on December 25,1871; they had three children: two sons, Day (1872--1889) and Leigh (1874--1901), and a daughter, Helen (1875--1940).
Split into simpler sentences: Bierce married Mary Ellen "Mollie" Day on December 25,1871. They had three children: two sons, Day (1872--1889) and Leigh (1874--1901), and a daughter, Helen (1875--1940).