For those who don't know Cassandra Cain, she was the 2nd Batgirl (technically 4th) before giving up the role to Stephanie Brown. She was also the first Batgirl to get her own self titled comic series.
Her parents were both notorious assassins. David Cain and Lady Shiva. Her father was the one responsible for her training and upbringing. She hardly ever spoke, but her actions spoke louder than words, and especially when it came to fighting. After saving the commissioner's life, she was then noticed by Bruce Wayne. She became the Batgirl and soon was adopted by Bruce Wayne. After killing her mother, Lady Shiva, she gave up the cowl to Stephanie Brown and fled the batfamily. Robin went in search for her, but that's where her story initially ends.