unit Unit1;

interface

  uses
    System.SysUtils, System.Types, System.UITypes, System.Classes, System.Variants,
    FMX.Types, FMX.Graphics, FMX.Controls, FMX.Forms, FMX.Dialogs, FMX.StdCtrls, FMX.Layouts, FMX.TreeView;

  type
    TTest = class(TTreeViewItem)

    end;

  type
    TTest2 = class(TTest)

    end;

  type
    TTest3 = class(TTest2)

    end;

  type
    TForm1 = class(TForm)
      TreeView1: TTreeView;
      procedure FormCreate(Sender: TObject);
      private
        { Private declarations }
      public
        { Public declarations }
        testvar1: TTest;
        testvar2: TTest2;
        testvar3: TTest3;
    end;

  var
    Form1: TForm1;

implementation

{$R *.fmx}

  procedure TForm1.FormCreate(Sender: TObject);
    var
      i: Integer;
    begin
      testvar1        := TTest.Create(Form1);
      testvar1.Parent := TreeView1;
      testvar1.Text   := 'TESTing too';

      testvar2        := TTest2.Create(Form1);
      testvar2.Text   := 'TESTing';
      testvar2.Parent := TreeView1;

      testvar3        := TTest3.Create(Form1);
      testvar3.Parent := TreeView1;
      testvar3.Text   := 'TESTing toooo';

    end;

end.