Complex sentence: He calls himself the same name as Serapion the Elder called himself--the distinction between "Younger" and "Elder" was introduced later by others after it was realized that they cannot be the same person.
Split into simpler sentences: He calls himself the very same name as Serapion the Elder called himself. The distinction between "the Younger" and "the Elder" was introduced later by others after it was realized that they cannot be the same person.