Grandma BubbleBottom may be known for making meatballs.
She may have been born to SpongeBob's great grandmother.
At some point, she married Mr. BubbleBottom.
At some point, Mr. and Mrs. BubbleBottom had Margaret BubbleBottom. They may have also had another child.
"A Pal for Gary"
"SpongeBob's Last Stand"
While being arrested for playing an unlicensed sitar, SpongeBob mentions how his grandma gave him the sitar without a license. He may have been referring to Grandma BubbleBottom.