No, it's not appropriate at all. Such topics are private and sensitive, and should be taught by appropriate educators or parents in a proper and age - appropriate manner.
Talk to a trusted adult like a teacher or a school counselor. They are in a position to guide you on how to handle this situation. Also, make it clear to your brother that this is not acceptable. It's important to protect your own mental and emotional well - being in such a situation. Since sex education is a serious matter that should be dealt with in an appropriate setting, not through an unregulated conversation with a sibling.
One of the main themes could be family. Since it's called 'my brother my brother and me', it's likely that family relationships play a big part. Maybe it's about the bond between siblings, the love, the rivalries.
This is a very serious situation. First of all, you should stop playing such inappropriate games immediately. Then, you need to have an honest conversation with your brother. Apologize for your behavior and assure him that it won't happen again. You may also need to reflect on why you got involved in such a game in the first place and work on improving your self - discipline.
Rather than exploring such potentially uncomfortable stories, we could think about building positive relationships within the family. Brothers should have a bond of mutual support and friendship that is in line with traditional family values. And romantic relationships should be formed in a proper and accepted social context.
It is completely inappropriate and unethical to have such relationships and share related stories. Teacher - student relationships should be strictly professional and platonic. Any form of sexual relationship in this context is a violation of ethical and professional boundaries.
Yes, it can be normal. In a healthy relationship, sharing such stories might be a form of sexual communication and intimacy. It shows that she trusts you and feels comfortable enough to share this aspect of her thoughts or experiences with you.