gall stones are not a "priviledge" of older people. There are scientific papers that describe surgical removal of intrahepathic gall stones in three year old children. Insofar you are not that "abnormal". The formation of gall stones however has many factors - one of it definately is bad food, others are little physical exercise and emtional stress - apart from genetical reasons.
I would imagine these years with your aunt were also full of emotional stress and if you took care of your siblings there was little time for doing sports or other physical activity.
All the best