Will i be a bad person for doing this? ........?

I'm going to be honest and straight forward with you, That will Be totally WRONG if you dated your best friend's man!! Why would you do a thing like that considering the fact that your friend's heart is wrapped up in this guy. As a good friend, you should sacrifice your feelings and allow your bff to be happy with her bf. as for him, he's totally wrong for wanting to cheat on her. and if you decide to go with him you aren't making a wise decision because if he considers cheating on your friend know that he'll consider cheating on you too...then you'll have a double lost... your best friend and her bf! Think wise.