You can read all about him here, two articles – the first, about his earlier life, William the Marshal: The Greatest Knight, and the second, William the Marshal: 1st Earl of Pembroke & Regent of England

Do you have dates for John the Marshal & William Marshal? Was it, perhaps, that William inherited John’s office and title?

Whenever the aristocracy adopted surnames doesn’t change when the great bulk of people got them.

I’m not so sure we should credit the Normans for surnames — not in the sense of family names passed down from fathers to all their children. The practice of adding a sobriquet was usual practice before the Normans, e.g., the Anglo-Saxon king Edward the Confessor (who lost to William the Conqueror) and Scots king Malcolm Canmore. William’s father was Robert, often called Deville, but more often “the Magnificent”. William’s sons all had different 2nd appellations, as did Henry’s.

I believe we didn’t see true surnames in England until the Crusaders came through Venice on their way back from the wars and copied the practice in the late 12th century. Still, only the aristocracy had that privilege; it wasn’t until the Black Plague’s aftermath that common people needed to be told from each other so their taxes could be collected. That puts the date sometime in the reign of Edward III or after — mid-14th to early 15th centuries — about 300+ years after the Battle of Hastings.