In the show Family Matters with Steve Urkele, whatever happned to the sister Judy Winslow did she die or what?

In the beginning of the tv series they had another daughter named Judy, but as the series went on Judy seemed to disappear and there was never any more mention of her in the series or of Aunt Rachel either, but they still had her son RIchie. What the heck happened there?? Anyone know?