Grandma Higurashi

 was the late wife of Grandpa Higurashi, mother of Mr. Higurashi, mother-in-law to Mrs Higurashi, grandmother of Kagome and Sōta, and posthumous grandmother-in-law to Inuyasha. She died soon after her son was killed in the car accident, which left her husband as a widower.

Trivia

 * Grandma Higurashi is a novel-exclusive character and was never mentioned in the InuYasha manga and anime.