Someone will be offended regardless. There is going to be issues and awkward moments and possibly a broken friendship. So, if you think it’s worth it, then, by all means. But that in itself is a lot of drama on a new relationship. However, I think that you need to follow your heart. Although it is never the ideal situation when you date your ex’s friend, let us be realistic – they are exes, which means you are no longer in the picture.
As long as some time has passed and you have determined that you really have strong feelings for each other, then I say go for it. Sure, it will be awkward awt first but the reality is people are not property. You can’t help who you like at times.
If it is there, it is there. Don’t deny your feelings, you only live once. People make up too many rules and spend to much time defining what they feel is morally-correct. There shouldn’t be a problem dating a friends ex when it’s completely over not the day after they break up- that’s just cold. Maybe months or years later. Just don’t be too obvious, don’t rub it in their faces; be discrete in their presence.
People have a somewhat loose definition of the word “friend”. Just because someone is in your circles and you talk/deal with them on occasion does not make them your friend. So, if you dated their ex, there would be no problem.
As for your ride-or-die friends, an ex should be a no-go area. If for nothing else, then for the fact that you might have to talk about them and it can be complicated.
Case One: You knew the guy and girl while they were still a couple. Strictly deal with the girl as if she has rabies. Don’t even be buddies with her.
Case Two: You got to know them after they broke up. Still slippery ground, but can be negotiated. It is recommended to inform the dude, if he is your valued friend.
Case Three: You only got to know after you and her started dating: in this case, her ex will be fine. Just do not rub it in his face.
Case X: The man is your buddy but not the kind that you would give up a girl for. You are free to do everything your back-stabbing mind can come up with.
It would not be a wise move unless you are ready to be misunderstood, especially if they broke up on bad terms. Chances are, he shared his grief with you when the breakup happened and being his friend, you comforted him.
Dating his ex would feel like a disrespectful slap.