On wedding night. Husband: No one of us should open the door tonight for anyone. Who ever be there. She agreed. After some time his father and mother knocked the door. They both looked each other. His parents went back. Next knock was from wife's parents. They ask their daughter to open the door. She looked at his husband. Tears flooded her eyes. She said, I can't keep my promise. Her husband gave her a smile and she opened the door for her parents. In their happy life, there born twin sons. After couple of years born a daughter. The time came their both sons got married. At the time of their daughter's marriage, the husband gave a big party. The wife asked him, why a big celebration at the marriage of our daughter only? He replied: When we grew old and will knock her door, by sure she will open the door.