There can be a challenge in adjusting to the new dynamic. As best friends, they were used to a certain level of equality and informality. But in a romantic relationship, there might be power dynamics, jealousy issues, and different levels of emotional intimacy. It takes time to figure out how to balance these new aspects while still maintaining the core of their friendship.
One common challenge is the fear of ruining the friendship. Since they were friends first, they are afraid that if the romantic relationship doesn't work out, they will lose that precious friendship forever.
A major challenge is the fear of losing the brother's friendship. The best friend might be afraid that his relationship with the girl will cause a rift between him and the brother. And for the girl, she may be worried that her brother will be angry or disappointed. There's also the aspect of secrecy. In the beginning, they might feel the need to keep their relationship a secret, which can be really hard. They have to be careful not to let the brother find out accidentally. And if the relationship progresses, they have to figure out how to break the news to the brother in a way that won't cause too much drama.
A major challenge can be adjusting to the new role. You've been best friends for so long, and suddenly being lovers means different behaviors, like more physical intimacy and different ways of communicating emotions. It can be awkward at first. And if you have different love languages, it can cause misunderstandings. Say, if one person shows love through acts of service and the other through words of affirmation, it might take time to understand and adapt to each other's needs in a romantic relationship when you were so used to the simplicity of friendship.
There can be problems with outside opinions. Your friends and family might have a hard time adjusting to the new relationship. They might have always seen you two as just friends and might be skeptical or even negative about the change. Also, within the relationship, you might struggle with setting new boundaries. Since you were so comfortable as friends, it can be difficult to figure out what's okay and what's not in a romantic context.
One common element is the long - time acquaintance. Since they are best friends, they usually have known each other for a long time. Another is the moment of realization, like in a dangerous situation or during a time when they support each other deeply. For example, in a story I know, the girl realized she loved her best friend when he took care of her when she was ill.
Another challenge is dealing with other people's opinions. Sometimes friends or family might not approve of the relationship because they are so used to seeing them as just friends. In some cases, there could be concerns about how the dynamic of the friendship will change in the relationship. For instance, if they used to share everything freely as friends, in a romantic relationship, there might be new insecurities and jealousies that could make things complicated. Also, if they break up, it's not just a simple end of a relationship but could mean the end of a very deep friendship as well.
Here's one. There were two best friends, Anna and Jack. They were always there for each other. Anna was dating someone else for a while but always found herself thinking about Jack more. After she broke up, Jack was there to comfort her. During that time, they shared a lot of deep conversations. Jack then noticed he had fallen for Anna. Anna soon realized the same. They were hesitant at first but then embraced their feelings and are now a happy couple.
Another challenge is dealing with the opinions of mutual friends. They might be shocked or not support the relationship at first. They could be used to seeing you two as just friends and might find it hard to adjust to the new dynamic. Also, if things go wrong in the relationship, it can have a ripple effect on the whole friend group.
Communication problems. If the best friend and the girlfriend don't communicate well, misunderstandings can occur. Like when the best friend tries to give advice about the relationship but does it in a wrong way that the girlfriend takes as interfering. There was a time in my life when my best friend told my girlfriend she should be more 'chill' about me going out with the boys, and my girlfriend thought he was being rude.
One big challenge is the fear of losing the friendship. If the romantic relationship doesn't work out, it might be hard to go back to being just friends. Another is that other friends might have different opinions and that could put pressure on the relationship. For example, some friends might think it's a bad idea and try to talk them out of it.