Those brothers who usually have a good relationship with us don't have to be too polite when playing together, that is to say, don't be too polite. Being too polite will make people feel a little estranged, just like two people are very unfamiliar, so we will not be too polite or polite when interacting with brothers or good friends, which means it is normal and it will be more natural to be together. If we treat people with courtesy, we can say that we can treat our elders or people older than ourselves or generations, because it is necessary and we should do the same. For brothers or close friends, we don't need to use the word "close friends" or this form to associate with them, because they don't care so much, and they don't care so much. As long as you interact with them normally, you can treat them normally.
But in some more formal occasions, such as they are very important occasions or we are very important occasions, we should treat them with etiquette or some more formal manners. After all, it is a very formal occasion. If we don't do this, it will not only make them feel uncomfortable, but also make others feel wrong, so although we are good friends or brothers. Politeness is also necessary in some formal occasions, but in normal or private occasions, you can still make a joke or something. So as long as it is not a formal occasion, or two people, as long as there is no feeling, you are welcome. Think about it. In fact, we are the same with those good friends in our life, so I believe we don't need to be too polite at ordinary times.
So different occasions can be different ways to get along. For example, being polite to good friends in private is a bit out of place for this era, and it is too casual and embarrassing in formal occasions.