ISomeInterface = interface
  end;

  TSomeClass = class(TInterfacedObject, ISomeInterface)
  private
    //class var FCount: integer;
    FSomeObject: TObject;
  public
    constructor Create;
    destructor Destroy; override;
  end;

constructor TSomeClass.Create;
begin
  inherited;
  FSomeObject := TObject.Create;
end;

destructor TSomeClass.Destroy;
begin
  FSomeObject.Free;
  inherited;
end;

function CreateSomeInterface: ISomeInterface;
begin
  Result := TSomeClass.Create;
end;

procedure TForm1.Button1Click(Sender: TObject);
var
  Obj1, Obj2: ISomeInterface;
begin
  Obj1 := CreateSomeInterface;
  Obj2 := CreateSomeInterface;
  try
    {}
  finally
    Obj1 := nil;
    Obj2 := nil;
  end;
end;