How to remove mdi form child form title icon in C#

It has to work this way, because Windows does not have any other place to put these buttons. Anyway if you want to hide the icon you can do it from code, when your MDI form is loaded or when you change status to maximized by adding this code

{
this.ControlBox = false;
}

Note : With this option you must create a button or shortcut to close your MDI form.

You can also try Devexpress's XtraTabbedMdiManager control,do what you want in a very easy way, in addition to many other configuration options.