But was Varys working to help the Targs? We know he was plotting with Mopatis. But we also know that he did in fact pass on the news of the Targs alliance with the Dothraki, he passed on the orders for the death of Dany, it seems to me he was playing both sides against the middle to make sure he was on the winning side.
Besides, the third head of the Dragon will probably be a Blackfyre, they have been very little represented in the series, and we know Bittersteel was exiled to the free cities, along with Egg's brother......
Also, if anyone hasn't read the Tales of Dunk and Egg, they should read them forthwith.
I like saying forthwith.