Uncle Gary's Wife is the unnamed wife of Gary O'Neal. She is an Asian Hindu. She made a brief appearance in the episode The Real Grandma. Her difference in race and religion is something that not all members of the O'Neal family is entirely on board with.
At the end of the episode The Real Grandma, Eileen was fed up with Agnes and her bigotry toward Kenny, so she kicked her out of their house and forced her to live with Uncle Gary. Given that this is the wife of Uncle Gary, she knew that Agnes would have a Hell of a time there and would hopefully learn a little tolerance for diversity in the process.