Naughty humor: Sometimes, boys may draw closer to each other in some naughty and humorous ways, and enhance the intimacy of the relationship through some humorous or playful actions. He may think that this can create some relaxed atmosphere and make the communication between you more relaxed and happy.
Express self-confidence: Some boys may express their self-confidence by showing their bodies or some aspects. This doesn't necessarily mean that he is seeking sexual attention, but it is more likely that he thinks you can appreciate his all-round side.
Communication needs: He may think that some humorous ways, such as showing his little brother, can attract your attention and deepen communication between you. This may be that he tried to express his emotional needs in a very direct way.
Sexual demand: although this possibility is relatively small, it cannot be completely ignored. He may try to convey some sexual needs or expectations in this way. However, in any case, this kind of communication may not be appropriate. If you are not happy about it, you should express your feelings frankly.
Faced with this situation, I suggest you think calmly first and communicate with your boyfriend through open and frank communication as much as possible. Ask him why he chose this way to express himself and what his real intention is. Share your feelings and emphasize your needs and expectations for communication. Through real dialogue, we can better understand each other's ideas, thus better solving problems and maintaining the healthy development of our relationship.