It depends on the context and on the people involved, but usually it's at least a little bit fucked up.

Also that is a sad bottom.

What kind of split did they have? It's kinda fucked up, but if they split up mostly amicably it's probably okay.

I'd be worried about bringing them around each other. How much time do you spend with your best friend irl? Could you successfully segregate the two? Did your buddy break up with her because she's a crazy bitch? all important factors to consider.

>>17358282
They aren't your best friend if you would go out with their ex.

>>17358296
This

You will most likely not have a best friend anymore. Unless he doesn't give a fuck about her or wasn't too serious. If they were really into monogamy and not into sharing partners, it will not bode well for you

>>17358286
>>17358287
>>17358296
It wasn't a bad break up really. Friend just was too busy all the time so they split.

>>17358317
How long did they date? It's hard to gauge if it would just be weird at first or if he would hate you for it. Or if she'd want you to hang around with your friend, sounds like she got the shit end of the stick. Just doesn't sound good.