All real relationships have faults, whatever the cause, what really matters most is the outcome. Relationships end all the time and new ones are also formed. Which is why its important to know when and who you can start a relationship with. Especially when it comes to dating a friends ex.
Personally, I think that it depends on the kind of relationship you have with your friend. And on your set of values and morals. Often we hear stories of friendship’s that ended because friends dated each others ex boyfriends and it seemed as if it had been planned.
I would advise a person to think deeply about what they are about to do. And to consider the impact it will have on their friendship. And if you are close to your friend, ask for permission before just jumping into something.
After all, friendships to me are more important than guys. And what a shame it would be to lose a friend over a relationship, especially if it ends later down the line.