Complex sentence: They had daughter, Marion Abigail Cook, in 1900, and a son, Will Mercer Cook, in 1903, who became a professor at Howard University, and then United States Ambassador to Niger and Senegal.
Split into simpler sentences: They had daughter, Marion Abigail Cook, in 1900, and a son, Will Mercer Cook, in 1903. Their son became a professor at Howard University and United States Ambassador to Niger and Senegal.