A boyfriend can act as a mediator in a friend's group. For instance, if two friends in the group have an argument, he can use his objective view to help them resolve their differences. He might offer practical solutions or just be there to listen to both sides.
It's highly unethical. Consider the situation from your best friend's perspective. She has an emotional connection with her boyfriend, and by getting involved sexually with him, you are not only breaking her heart but also ruining the bond you have with her. This kind of behavior is not acceptable in any healthy relationship dynamic, whether it's friendship or romantic relationships.
These kinds of stories often involve complex ethical issues. In most cases, having a sexual relationship with your best friend's boyfriend is clearly unethical. It betrays the trust of your friend and can cause great harm to the friendship. However, in some fictional stories where there are special circumstances like the best friend was already in a bad relationship and had given some form of consent, it still makes for a morally gray area.
There was a situation where a boyfriend in a friend's group was really into photography. He started a project to take portraits of each friend in the group. It was a great way to get to know everyone better on a personal level. Through this, he learned about their dreams, hobbies, and insecurities. This activity brought the group closer together and also made him more accepted as part of the group.
My best friend's boyfriend was an artist. He often painted portraits of her. Once, for her birthday, he organized an exhibition in a small local gallery with all the paintings he had made of her. It was a really sweet gesture. Many people came to see the exhibition and my best friend was over the moon. This not only showed his love for her but also made her feel special in the eyes of the public.
One of the main consequences is the loss of your best friend. No one would be okay with their friend having sex with their partner. Your friendship will likely be broken. Also, it can create a lot of drama in your social circle. People will take sides, and there will be a lot of gossip.
If she gets jealous when you talk about your time with your boyfriend or if she tries to undermine your relationship in some way. For example, she might say things like 'He doesn't seem that into you' or 'You two are so different, it won't last'. These are all red flags that she might have an ulterior motive regarding your boyfriend.
Well, first of all, communication is key. If you suspect something between your best friend and your boyfriend, have an honest talk with both of them. Maybe it's just a misunderstanding. For example, I once thought my best friend and my boyfriend were getting too close because they always texted. But when I talked to them, I found out they were just discussing a surprise for me.
I'm not sure which book you're referring to. However, if you can provide more background information or specify the type you are looking for, I will try my best to provide you with relevant recommendations.
One story is that they were best friends since childhood. They knew everything about each other. One day, the guy realized he couldn't imagine his life without her. So he took her to their favorite park and just blurted out his feelings. She was surprised but happy as she had been secretly in love too.