There is this old saying that Lord Sun and his wife Goddess Chhaya bore two children, son Lord 'Yama', and daughter Goddess 'Yamuna'.
Every year Yamuna insisted her brother to come to her house for lunch, but due to his responsibilities (taking note of death of human beings), he always had to excuse himself from the visit.
Once Goddess 'Yamuna' got very angry and was upset over his brother and that year she didn't invite him for lunch.
