I think I am falling for my boyfriends brother..?

Its probably best to leave your boyfriend if you dont love him anymore, and tell him youve fallen for his brother because you feel you have more in common with him (assure him nothing happened between you and his brother dosent even know how you feel)... then a week or so later tell his brother how you feel and see how it goes. I cant guarentee he will respond afterall you have gone out with his brother so it will be wierd, not to mention a direct violation of the bro-code but if you ask your ex if its alright and get his blessing it will be fine.