I think this post says something about his age http://www.swtor.com/community/showthread.php?p=9347029#edit9347029 "Then, Vitiate abruptly stops the war, proposes a treaty claiming seemingly-random planets, and starts the Cold War. An obscure step in his plan to complete the ritual? Makes sense, though if we look at how old Valkorion's children appear to be, they'd be getting born right around this time... coincidence?"
The treaty was made in 3653 BBY, Sacrifice trailer takes place in 3637 BBY (i could be wrong though), so the twins were around 16 then