Since we have a couple of weeks still before the start of Season 2, shall we have some fun speculating on who this young man might be? A new character created by GRRM for the HBO series because of a plot line we don't know about?
He's the youngest son of Tywin Lannister when Tywin secretly wed a high born lady on the 10th anniversary of his beloved Joanna's death. He never told his family about her because he didn't want them to know he was more human than he ever wanted to admit, and needed the touch of a loving woman. Oh my, the things we do for love!
In the end, it will be Alton who is the Valonqar, because Jaime and Tyrion are such loved characters GRRM decided to spare them that role.
Have fun! I don't think this is fan fiction, HBO should tell us who he is!
Which Season 2 casting video?