Complex sentence: He was unmarried and the viscountcy passed to his half-brother, Victor; upon the death of the 3rd Viscount, the viscountcy is expected to become extinct, as the 3rd Viscount has no issue.
Split into simpler sentences: He was unmarried and the viscountcy passed to his half-brother, Victor. Upon the death of the 3rd Viscount, the viscountcy is expected to become extinct, as the 3rd Viscount has no issue.