Autumn Tale is very much a Korean drama - love triangles, deceit, jealousy, hardships, etc… Be ready to cry, a lot!
Drama begins with two teenage girls that find out they were switched at birth. One raised in the wealthiest family of the area, and the other with a struggling single mother and abusive brother. They switched back the children to their real families, and go on to live one another’s lives. The wealthy family moves to the States with their real daughter and son, leaving behind the girl they had raised from birth. Years later, the brother returns to Korea with his family to find his long lost sister. Sad ending though, be prepared! 
The whole series is here.
