Empty nest syndrome - Compare a house with a nest. When a bird leaves the nest, then the other birds feel sad because that bird is leaving. This implies in the emotional human world also. This idiom signifies the pain of the parents when their kids are leaving the house to do work or study or something like this.
1. His parents began crying when she left the house, and I could see the empty nest syndrome.
2. Every parent has an empty nest syndrome when the kid leaves the house.
3. When Sheela left her house during the ‘bidaai', her parents also had the empty nest syndrome.