Brothers saving or destroying their brother seems to be a common theme in Lost.
We've had Mr Eko saving his brother Yemi and Yemi eventually saved Mr Eko from imminent arrest and gave him a chance to put his life back on track.
We've also had Charlie's brother, Liam, kinda introducing Charlie to drugs and yet the druggy brother eventually went all responsible/respectable with the house, wife and kids and it was Charlie who ended up on the slippery slope with drugs and couldn't give them up (until he was helped by Locke).
We now have Jack with a sister that he knew nothing about - could this theme of saving a sibling be repeated? Could Jack save Claire or could Claire save Jack? Jack now knows about Claire but Claire didn't know about Jack and if she is dead, will possibly will never know about Jack. That's sad thinking about it! (Boo-Hoo)!
Are there other brothers and sisters on the island that we don't know about yet?
See you in another life Brother seems to take on a whole new significance when looked at from this angle.
I shall now go way out on a limb and speculate that Desmond is Jack's brother!!!!

