I feel like it isn't that uncommon. Might just be that evil mother-figure characters don't have better titles to disguise their relation to the main character. A lot of the greek stories, for example, had kings, generals, gods and priests filling the evil father-figure roles.
I'm just spewing nonsense, but it feels right.
D
Deleted member 1244
"I am not an evil step mother, I am just an evil mother that stepped up"
I'm just spewing nonsense, but it feels right.