He is described as being a sturdy man.
He is the father of nine children, the eldest being Else Grinwell.
Master Grinwell shelters Rand al'Thor and Matrim Cauthon when they're on their way to Caemlyn in exchange for work in the farm. He loans them clothes and offers them the barn for sleeping, but Mistress Grinwell convinces him to give them Else's room.
At night, Rand and Mat play with Thom's instruments for the family.