The Dwarfs' Mother was a female dwarf.
This dwarf woman was the mother of Doc, Grumpy, Happy, Sleepy, Bashful, Sneezy and Dopey, the Seven Dwarfs living in a cottage in the Black Forest near the Kingdom of Snow White. She appears to have died, along with her husband, while her youngest son Dopey was still a child, an event which deeply scarred Dopey.
Behind the scenes
The Dwarfs' Mother's existence is implicit based on that of her seven sons in Snow White and the Seven Dwarfs (1937), and one can deduce that she died early from Dopey's need of Snow White to fill the role of a mother as shown most glaringly in The Seven Keys of Danger.
Her death was meant to be the emotional driving force of an unproduced Snow White and the Seven Dwarfs prequel that was to be directed by Mike Disa in the early 2000's. According to Disa, Dopey was meant to stop talking after being traumatized by her death, though this surprisingly dark concept cannot be considered canon, as it contradicts a line from the original film.