Sir Gaheris was the son of King Lot of Orkney and his wife Margawse, sister of King Arthur, before being knighted he was squire to his elder brother Gawaine.

Sir Gaheris married Linnet on the day his brother Gareth married her sister, Dame Lionesse, of the Castle Perilous.

The two brothers were slain in the struggle following the rescue of Queen Guenevere from the fire, though this was by accident as Sir Launcelot did not recognise them in the crowd. Sir Gawaine for a long time held Sir Launcelot in bitter hatred.