The Doctor felt his hearts stop almost for a second. So she was a time lord. That meant he was closer to finding out if she was his sister or not. He looked at Jack. He saw the surprised on Arwens face, he had always thought him and the Master were the last two left. But if Arwen was his sister maybe he wouldn't feel so lonely. He knew the Master hated him. He knew they needed to do a DNA test to make sure.
"Its ok Arwen," he whispered.
The Doctor looked at JAck "Suppose just leaves a DNA test."