pursuing relationship with someone else's friend with benefits?

ok, so here's something I'm actually interested in knowing what people think...

If there is a girl, and she has a boyfriend, then usually you should stop pursuing her as a potential girlfriend.

How about if they aren't bf/gf, but instead friends with benefits. what do you people think about this? does this seem wrong to you? because if you end up in a relationship with that girl, then you effectively homewrecked a fwb relationship right?
and different question, how about your friend's sister? curious about this one too?

Death and Rebirth are a primary force in this universe.

Relationships are wrecked, and then a new one is created, just like literally everything else.

Knowing this, what of the issue?

You want to pursue someone? Go ahead.

These ideals we have about what we should do and what we should not do are not grounded in the understanding of our existence, they are grounded solely in maintaining the "status quo"; this mental construct.

In other words, men and women concerned with "shoulds" and "should nots" have betrayed themselves in favor of the acceptance of what this "society" would like you to do. These so-called saintly folk aren't interested in your real enjoyment, or even in their own enjoyment. Only so long as they obey these ideals, that they have forgot were only ideas.

These people are interested in Death, and yet preach about Life.

If you want to wreck relationships, you will probably get into some sort of trouble, either externally, or internally. Or maybe not. Trouble is apart of the game. And it is true, that if you do things with malicious intent, then you will reap malicious rewards.

That's why it's important, relatively speaking, to do things out of understanding. But this has nothing to do with morals, religion, or society.

The catch, is that the relationship will have been wrecked eventually. Either by death, loss of love, distance, career...You. What's the difference? lol.

Simple answer is do what you choose to do as long as you're willing to take on the consequences.

Too many people shy away from doing things because of consequences

a scenario like this will most likely never happen. theres nothing to home wreck.

For me, it's wrong not in the sense that I just home wrecked a FWB arrangement; instead, it's wrong in the sense that I can't fathom why I would want somebody else's sloppy seconds - and on top of that, to think I would really accomplish an actual relationship with a girl who already seems perfectly fine not really being in one.  It would seem to be a rather trivial pursuit, don't you think?

Everything is a trivial pursuit.

If it's a friends with benefit relationship, there isn't anything that they would lose since they didn't want each other in the first place. I mean a permanent partner. Whatever, go for it.The story would be slightly different if it was an open relationship though, maybe.

 In my experience some people in FWB relationships have "rules". Idk, but it will complicate things less if you just talk to her. There's nothing wrong with pursuing IMO, because it's not really YOUR fault if you "home wreck", since it was the chicks choice. 

I... wouldn't be interested in pursuing her in the first place LOL

Wow most of the time the FWB will turn into an actual relationship as they develop feelings for each other.
Pursuing this girl would end terribly for everyone in my opinion.

The sibling of a friend one isn't as tough but it can go either way.
If you genuinely have feeling for them then you may get the blessing of your friend.
No one would be upfront about this situation however and tend to go behind their back for a little while.

I think I have a solution to all your problems. Get money, move to a state where prostitution is legal.

@Ninshark: It would be wise to leave that alone. Rhetorically speaking with the situation you presented who does that. In my head being honest that feels kind of desperate. Have more self-confidence in yourself, or to the person this applies to! No disrespect intended but you or the guy you're referring to can't "save" her.