<P> Billy Kapowski is Kelly's baby brother, whom she places in the care of her friends in the episode "The Babysitters" so that she could have her cheerleading picture taken for the school yearbook . Zack is often left alone with Billy as the others make excuses or have other commitments to attend to . Because of this, Billy and Zack bond quickly to the point where Zack distrusts anyone else to care for the baby . He is forced, however, to allow Jessie and Lisa to look after him in their Home Economics / Parenthood class . They lose track of Billy when Screech goes to fetch Billy for Zack but mistakes a doll for the baby . The gang eventually find him in Mr. Belding's office, and at the end of the episode he speaks his first word: "Zack ." </P> <P> Another brother of Kelly's, he disrupts the end of one of Kelly and Zack's dates . Kyle later dumps water on Zack from the second floor of their house after Kelly decided against going steady . </P> <P> Nicki Kapowski (portrayed by Laura Mooney) is Kelly's tomboyish little sister who develops a crush on Zack . She becomes convinced that Zack feels the same way after he mixes up her phone call with Kelly's (while running the "Teen Line"). Although she is only thirteen and in the seventh grade, she nonetheless shows up at Bayside High to visit Zack, sporting a more feminine look and demanding a kiss . After trying various ploys to turn her off (including dressing up like a geek and trying to gross her out with a pet spider), Zack finally has to tell her the truth: he isn't interested in her; he is in love with Kelly . More angry than hurt, she insults Zack for trying to scare her away instead of having the courage to tell a thirteen - year - old girl how he really feels . </P> <P> Harry Bannister (portrayed by Dean Jones is Kelly's grandfather from the movie Saved by the Bell: Hawaiian Style . He invites Kelly and her friends to stay at "The Hawaiian Hideaway", a rustic hotel in Hawaii . However, someone else is out to buy his land and build a hotel / resort complex, and the gang has to save it . </P>

Who played kelly's little sister on saved by the bell