It's also a part of the Criss-Cross Series by Quasar http://www.wraithbait.com/viewseries.php?seriesid=156 but it's not mentioned until the 6th story of the series.
There's been a few identical or similar searches here: John is Jack's son (http://community.livejournal.com/sgagenrefinders/728234.html), John is related to Jack (http://community.livejournal.com/sgagenrefinders/516842.html) and Jack O'Neill, another member of SG-1, or a member of the Atlantis expedition is John's father/relative (http://community.livejournal.com/sgagenrefinders/277425.html).
There's Crossing Paths, which is the sixth story in the Criss-Cross Series - the whole series is interesting, but the sixth is the one that deals with John and Jack specifically....
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Date: 2011-01-29 12:59 am (UTC)The Connection by Keikokin
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Date: 2011-01-29 05:24 am (UTC)no subject
Date: 2011-01-29 06:56 am (UTC)http://www.wraithbait.com/viewseries.php?seriesid=156
but it's not mentioned until the 6th story of the series.
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Date: 2011-01-29 07:27 am (UTC)no subject
Date: 2011-01-29 11:37 am (UTC)no subject
Date: 2011-01-29 04:09 pm (UTC)no subject
Date: 2011-01-29 04:10 pm (UTC)no subject
Date: 2011-01-30 12:42 am (UTC)Summary: John Sheppard has the ATA gene for a reason, and the answer is at the SGC.
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Date: 2011-01-30 12:42 am (UTC)http://www.squidge.org/keikokin
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Date: 2021-02-07 06:56 am (UTC)no subject
Date: 2021-02-13 11:12 pm (UTC)