I really enjoyed this, it was very touching. Thank you. As for the tune, I would guess that it was Danny Boy, which is always what comes to mind when I see Daniel. :)

I have no idea what the song was. Hasn't enough time passed that you tell us, now? You did a good job of capturing Jack's feelings, except there was no mention of Charlie. I think the time line is off a little, too...maybe it should have been his second Christmas without Sara instead of the first one. Charlie had died not too long before the first Abados mission. Jack came back from that mission to find Sara gone. It was a YEAR before the second mission when he brought Daniel home and SG-1 became a team, so there would have to have been at least one Christmas in between, wouldn't there?

Loved it. Very good Jack fic. You captured his feelings so well, especially the way he still loves Sara... Really nice. As for the tune, I have no idea... :(