Devlin was born in Cookstown, County Tyrone, to a Catholic family, where she was the third eldest of six children born to John James and Elizabeth Bernadette Devlin. Her father raised her to hold Irish Republican ideals before he died when Bernadette was nine years old. Subsequently, the family had to depend on welfare to survive, an experience which affected Bernadette deeply. Bernadette's mother died when Bernadette was nineteen years old, leaving her to partially raise her siblings while also attending university.