The Citadel: FAQ

5.2. Why was Renly showing Ned the locket?

Renly makes this plain when he says to Stannis, "A year ago I was scheming to make the girl Robert’s queen." (II: 350) Robert tells Eddard that Renly has been telling him about Margaery’s beauty (I: 260). Clearly, Renly hoped that his source was correct in claiming that Margaery bore some resemblance to Lyanna, thinking that it would make it easier to entice Robert to bed and wed her. There is some argument whether Renly’s secondary intention was to attempt to bring Eddard into the conspiracy, but Eddard’s account (I: 233) does not suggest that Renly pressed the point regarding Lyanna, or discussed Margaery, any further once Eddard disavowed any resemblance between the two young women.