I dunno if this could be tied in with the event manager in the upcomming expantion or if it could be done indapendatly ,but what if firstly the name of your civ leader could have a lineage that married in to other civ leaders family or other lineages within your civ(these would be your great leader ).This could have reprecusions of happiness within your civ and other civs.This could also impact trade aggreements ,city trades ,technology trades etc.
As I write this the idea is evolving ,if the royal family marries into the family of a great scientest within your civ ,this lineage could marrie into another civ giving you acess to science trade that other wise wouldnt be available because a difference of religion.
any way I put this out for discusion...