Complex sentence: Tiffany Leeds (Russell's sister) joined the act in 2012 and they performed at the Brighton Fringe Festival in May 2012 and were noticed by a talent scout for a large entertainment agency.
Split into simpler sentences: Tiffany Leeds (Russell's sister) joined the act in 2012. They performed at the Brighton Fringe Festival in May 2012 and were noticed by a talent scout for a large entertainment agency.