I was looking at my post from last year (below link) where the preacher in the wedding ceremony called out Lamont's full name as Lamont Grady Sanford. Then all of the sudden it hit me that maybe Fred also used "Grady" as his middle name where the middle G name would be Fred Grady Sanford. And the son Lamont Grady Sanford.

In the show, it was never mentioned what the "G" in Fred G Sanford really stand for, so this might be as close as we are going to get as what it stand for :)

https://www.sitcomsonline.com/boards/showthread.php?t=473527

Iirc, one show's dialogue revealed that Lamont was named Grady after Fred's longtime best friend, Grady Wilson.

For the show, Grady fits as family tradition and lineage. But I think Redd's brother's (and father's!) real name was Fred Glenn Sanford.

Since the character, Fred, was named as a tribute to Redd's brother, it could be either!