Here's my first contribution:
Assuming R+L=J, Sam and Jon are actually related to each other by marriage. Sam's mother is a Florent, Selyse Baratheon's first cousin, making Sam and Shireen Baratheon second cousins. Jon and Shireen would be third cousins; Rhaegar and Stannis are second cousins.
ETA: Continuing on with Sam, it might become significant, seeing as he's in Oldtown, that his aunt is the current Lady Hightower.
Edited by Apple Martini, 06 January 2013 - 12:59 AM.