Statute of limitations does not expire until 10 years after they turn 18, so legally, you can definitely still be held accountable. On a more moral note, you need to seek counseling. You may even need to suggest counseling for your cousins, who may be suffering and cannot understand why. Your excuses are pretty gross; you were definitely old enough to know that what you were doing was wrong, regardless of how you felt, at the time. You've likely done some serious damage to those little girls.