I really fancy my friends brother AND her boyfriend.?

how can i coax them both into a happy 3some/3way r'ship with me?also i dont think shes good enough for him(her boyfriend).her brother is 29,i'm 17,shes 19 and her boyfriend is 17.they are both really handsome guys.and i have had a crush on her boyfriend for ages.he was meant to be dating me but she stole him from me.