Sharing such a story is completely inappropriate and violates privacy and ethical boundaries. It involves very private and often sexual content that should not be casually disclosed.
If it's a 'girlfriend sucks my friends story', it might be that the girlfriend is very controlling and doesn't want her partner to spend time with their friends. She could be constantly calling or texting when they are out with friends, making the friends feel like they are intruding. This kind of behavior can really put a damper on the friendship and make the whole situation rather unpleasant for everyone involved.
One possibility is that the girlfriend is always trying to compete with the friends for the person's attention. She might throw tantrums when the person spends time with friends instead of her, and this behavior is what makes the situation seem like she's'sucking' for the friends. For instance, if they have planned a guys' night out and the girlfriend gets angry and tries to guilt - trip the guy into staying with her, it's not a pleasant situation for the friends.
Sharing such a story is completely inappropriate and unethical. It involves vulgar and inappropriate sexual content that goes against moral and social norms.
Immediately change the subject. You could say something like 'Hey, that's not a good topic. Have you seen any interesting movies lately?' This shows that you don't want to engage in such inappropriate talk. Also, it's important to convey that this kind of story is not acceptable in a normal conversation without being rude.
I don't really know the specific story. Maybe it started over a silly argument like who gets to use a certain dress first or something. But without more details, it's hard to say exactly what happened.
One possible consequence could be the breakdown of the marriage or the primary relationship. Trust is severely damaged when such improper behavior occurs.
It could potentially mean a story about something negative related to a friend's wife. Maybe it implies that there are some problems or unpleasant situations involving her, but without more context, it's hard to be certain.