Automatically Form Closing on Initializer form closing

Suppose there are 3 Forms , named form1,form2 and form3. form2 and form3 can be opened from MDI form menu. and as well as from form1's button click.

is there any possibility when form2 and form3 are opened from form1 not MDI. so that when we close form1 , form2 and form3 close automatically.

form1 is not MDI form. all three forms are opened in MDI form.