1、新建 FM(HD) 工程, 先添加 TLine(默认名称是 Line1);
2、在 Line1 选择状态下添加 Button1;
3、取消选择后添加 Button2

此时, Button1.Parent 是 Line1; Button2.Parent 是窗体.

unit Unit1;

interface

uses
  System.SysUtils, System.Types, System.UITypes, System.Classes, System.Variants,
  FMX.Types, FMX.Controls, FMX.Forms, FMX.Objects;

type
  TForm1 = class(TForm)
    Line1: TLine;
    Button1: TButton;
    Button2: TButton;
    procedure FormCreate(Sender: TObject);
    procedure Button1Click(Sender: TObject);
  end;

var
  Form1: TForm1;

implementation

{$R *.fmx}

procedure TForm1.FormCreate(Sender: TObject);
begin
  Button2.OnClick := Button1.OnClick; { TLine }
end;

procedure TForm1.Button1Click(Sender: TObject);
begin
  Caption := TButton(Sender).Parent.ClassName; { TForm1; 现在的窗体没有 Text 属性了 }
  Line1.Position.X := Line1.Position.X + 10;   { Btuuon1 会随同移动 }
end;

end.