Osoraku Kanojo wa Ore no Aniki o Neratteru

After being duped too many times by girls who merely wanted to be near his attractive elder brother, a high school boy has lost all faith in girls. He concludes that he will never again trust a girl after all of that. However, a lovely girl in his class started talking to him a lot all of a sudden. Is she merely attempting to reach his sibling as well? Or is she really referring to something else?