Yuma Simpson (née Hickman) is Homer's paternal grandmother, Mona Simpson's mother-in-law, and Marge Simpson's grandmother-in-law from "The Old Country", which bears similar characteristics to Ireland or Scotland. Most importantly, she was also the paternal great-grandmother of Bart, Lisa, and Maggie Simpson.
Yuma married Orville Simpson in the early 1900s. For a few years, they lived inside the Statue of Liberty, along with their sons, until the head of it was filled with too much garbage. Much of this story is questionable, as it is gained from one of Grampa's senile rants.