Complex sentence: They had one son, Miles Vorkosigan, who is the main protagonist of the Vorkosigan Saga-though, technically, they have "two" sons, or at the very least, a son once removed in Miles' clone brother, Lord Mark.
Split into simpler sentences: They had one son, Miles Vorkosigan, who is the main protagonist of the Vorkosigan Saga. However, they technically have "two" sons, or at the very least, a son once removed in Miles' clone brother, Lord Mark.