Friends obsessed with brother?

Ok so my friends are obsessed with my brother there always asking if the can come over not because they want to spend time with my but they want to chat with my brother.The other day my friend came over lets call her Lucy and she bursts into his room and just stands there staring at him.I come up finding my brother trying to get rid of her.He keeps telling me how annoying they are.My brother is a really good guy really kind nice good looking but when my friends come over he can turn into a really irritated person he gets really annoyed with them.My friends fight over him when Im not there and it ends up turning aggressive.The problem is my brother is dating a girl and if they find out I don't no what will happen there always like 'OMG What is your brother doing today' they always want to find out they stalk him on facebook and msn there always referring to him as fit good looking hot hunky! etc..its gets so annoying wherever I go all my friends talk about is my brother.They stare at him and are really random when they see him. There like 'his hair is so fit' 'I love his big green eyes' 'Omg did you see his top' etc.. my friends always ask me to ask his fave features on a girl and then when he said I like brunettes but he didn't mind all my blonde haired friends brought brunette hair dye.He has been dating this girl who my friends have no idea about for about 2 months now she is really pretty and really nice but I don't no how to tell my friends they will all start fighting and everything its so annoying