C# Distructor Issue

Question

I have an issue in my code which is : 

 

i have 2 classes Parent and Child

class Parent
{
   List<Child>  Childs1 = new List<Child>();
   List<Child>  Childs2 = new List<Child>();
   Parent()
   {
      // Some Code
   }
   ~Parent()
   {
       Console.WriteLine("Hello World!!");
   }
}

class Child
{
   // Some Code
}

 // Output :-

 

 Hello World!!

 Hello World!!

 

- Why the parent distructor is been called twice when  instantiated in the main after the           program is closed?