Twalin was born the day when Smaug claim Erebor as yours. Her mother was a beauty and kind woman of the Dale. Her father was a Dwarf who died that day, under the mountain.
Years later, when her mother move to the Lake-Town, their lives was difficult and her mother kept in secret her origin and race. She didn't want her daughter to grow up being despised by humans, but did not want her ignore her culture. She sang songs of the Dwarves, legends and stories his father told her when they were young.
When her mother fell ill, she told her the truth about her father. She made her promise that when she died, she would fetch her another family to the Blue Mountains, as she believed she could find some relative of her father.
Years later of the dead of her mother, Twalin began her journey to the Blue Mountains.