Like I said they need a third and he does fit in nicely. As a long shot thery of the third Targaryen I'd say Varris, but it is a giant long shot there. Not sure how he would fit though as his past is very mysterious to us. However Tyrion will find out about his true lineage this season if it is true. It would also mean he would have a higher claim to the throne than Danni too, but under Jon.