Complex sentence: He was a friend of Sidonius Apollinaris from their schooldays, and husband, married before 450, of Eulalia (?), born ca 425, a cousin of Sidonius Apollinaris, daughter of Thaumastus I (?).
Split into simpler sentences: He was a friend of Sidonius Apollinaris from their schooldays. He married before 450 Eulalia (?), born ca 425, a cousin of Sidonius Apollinaris, daughter of Thaumastus I (?).