Brianna is a sweet, innocent little girl who is hard not to like. She is first introduced in the episode, Chains, Part 1 in the Novacom Saga. She and her brother, Tony, used to live in the old building that stood where the Whit's End in Connellsville is now.
Her parents died in a car accident.
Brianna is the sister of Tony. Both of them eventually get taken in by the Mulligans.
She also has a cousin; not much is known about him except that he's an alcoholic.