Complex sentence: He eventually was remarried to Elizabeth Hamlyn Holdridge (1909--1998) in 1949, by whom he had an only daughter, Lucy Hamlin Dos Passos (b.1950), and he continued to write until his death in Baltimore, Maryland in 1970.
Split into simpler sentences: He eventually was remarried to Elizabeth Hamlyn Holdridge (1909--1998) in 1949, by whom he had an only daughter, Lucy Hamlin Dos Passos (b.1950). He continued to write until his death in Baltimore, Maryland in 1970.