Just because he doesn't know that Aaron is his nephew doesn't mean that for some reason he would be compleled to go.. Maybe in some way Aaron is a key to get back and gone.. Character connections and all are key in Lost..

Like I said before its probably not right but it is an idea to wake us all back up!

__________________
Please don't give up, Des. Because all we really need to survive is one person who truly loves us. And you have her. I will wait for
you. Always. I love you, Pen

DESMOND: I love you, Penny. I've always loved you. I'm so sorry. I love you!
PENNY: I love you too.
DESMOND: I don't know where I am, but--
PENNY: I'll find you, Des--
DESMOND: --I promise--
PENNY: --no matter what--
DESMOND: --I'll come back to you--
PENNY: --I won't give up--
BOTH: I promise. I love you.