Crud, I got him mixed up with Beren who gave Saruman the keys of Isengard. My bad...
Now that I've got it jolly well straight let's see about this:
Boromir of Ladros-> Barahir-> Felagund-> Galadriel-> Borondir*-> Cirion-> Boromir the Steward
*Borondir was the last rider of Gondor who made it to Eorl to ask for help. When he and the Eotheod passed by Lorien and Dol Guldur, Galadriel sent out a veiling mist to protect them. Borondir acknowledged her power as something good rather than ominous as the Eotheod thought it. So thats how they were connected. Aye yi yi, this was a good one...