Game of Thrones: Why Daenerys Likely Isn't the Last Targaryen After All

A lot has been made on Game of Thrones of Daenerys (Emilia Clarke) allegedly being the last Targaryen to survive Robert Baratheon's (Mark Addy) quest to wipe out the bloodline.

[...] what if Dany's family is still out there - and hiding right underneath our noses?