This theory might be pretty far-fetched, but have you ever heard of fen tao zhi ai (the love of a shared peach) aka manlove? There's this story of a Chinese court official, who bit a peach and found it sweet, so he offered the rest to his lover, the emperor/duke.

Does this mean that Renly is telling his brother to try it, he might like it? Because the shared peach is a symbol of homosexual love, I think.

/rambling soothsayer