In Geronimo Stilton who is Benjamin's mom?

It seems to be never revealed as far as I know!

Someone had answered previously that aunt Sweetfur might be the answer but I disagree; that would make Benjamin a cousin rather than a nephew.

It seems that either Ben's parents are both dead or unable to take care of the little guy since he's being taken care of by a great aunt and Geronimo once stated (in book #2) that if he died in a plane crash, little Ben would be begging for food never making it to college.