A “good knight of Scotland” who became a companion of the Round Table, being listed among the would-be-healers of Sir Urre. This is about all Malory tells us of him, and in the second reference his name is given as “Sir Gromere Grummer’s son”.
I do not think he should be identified with Gromer Somer Joure. Grummore Grummursum is a minor knight.
Source
Le Morte Darthur | Sir Thomas Malory, 1469-1470