아래 것을 사용해보세요
procedure TForm1.Button4Click(Sender: TObject);
begin
    Create_Form(TForm4, Form4);
end;

procedure TForm1.Create_Form(TCForm: TComponentClass; var Reference);
var
    AForm, CForm : TForm;
    Instance: TComponent;
begin
    CForm := TForm(Reference);
    AForm := Application.MainForm.ActiveMDIChild;
    if not(assigned(CForm)) then begin
       Application.CreateForm(TCForm, CForm);
       TForm(Reference) := CForm;
    end;

    if AForm <> nil then begin
       CForm.Top  := AForm.Top - 24;
       if CForm.Top < 0 then CForm.Top := 0;
       CForm.Left := AForm.Left - 24;
       if CForm.Left < 0 then CForm.Left := 0;
       AForm.SetFocus;
    end;
end;

hsr////////////////////////////////////////////////