Problem med Free i dbExpress

Har en tråd som ser ud som vist neden for, problemet er at når jeg sætter NewDBCon.Free
så Free'er den også min MyDBCon

unit tTestThread1;

interface

uses
  Classes, DBXpress, Provider, SqlExpr, FMTBcd, DB, Grids, DBGrids,
  DBClient, DBLocal, DBLocalS, StdCtrls, Spin, ExtCtrls, sysutils;

type
  TestThread1 = class(TThread)
  private
    { Private declarations }
  protected
    procedure Execute; override;
  public
    MyDBCon : TSQLConnection;
    NewDBCon : TSQLConnection;
    Tal : Integer;
  end;

implementation


procedure TestThread1.Execute;
var
  i : Integer;
begin
  FreeOnTerminate := True;
  i := 1;
  NewDBCon := TSQLConnection.Create(nil);
  NewDBCon := MyDBCon;
  if NewDBCon.Connected then
  begin
    with TSQLQuery.Create(nil) do
    begin
      SQLConnection := MyDBCon;
      while i < 100 do
      begin
        DisableControls;
        SQL.Clear;
        SQL.Add('UPDATE TestThread SET Tal = '''+IntToStr(tal)+'''' +
                              ' WHERE id = ''' + IntToStr(i) + '''');
        ExecSQL;
        EnableControls;
        inc(i, 2);
      end;
    Free;
    end;
  end;
  NewDBCon.Free; <----NÅR DENNE LINIE ER MED GÅR DET GALT
end;

end.