Prudence Crumplebottom

Prudence Crumplebottom is the deceased mother of Cornelia Goth, and Agnes Crumplebottom, the wife of Simon Crumplebottom, the grandmother of the infamous Mortimer Goth, and the great grandmother of Cassandra and Alexander Goth

Life leading up in The Sims 3
In The Sims 3 Prudence is already deceased her tombstone can be found in the Goth Family graveyard along with that of her husband, her son-in-law's parents and an unknown relative

Life leading up in The Sims
Prudence is now long dead and is likely buried in either the Goth Sr. graveyard or the grave yard of the younger Goth Family.

Life leading up in The Sims 2
Oddly Prudence's tombstone can not be found in the Goth Family graveyard or anywhere else for that matter so it is presumed that her tombstone was destroyed by someone, or that the creators of the game made a mistake.