He has the exact same death date as his putative father, Sir Robert Algore - seventeen years before his putative wife was even born, and some forty-three years before his putative son was.
Sir Robert Algore is generally said to have had only one surviving (legitimate?) child, a daughter Agnes.
The most likely answer is that he is not Sir Robert's son and his dates have been crocked.
Alternatively, he may have been extramarital, therefore ineligible to inherit - and his dates are still crocked.
