To dream of a brother is to dream about being supported by someone close to you. This could be a brother, another family member or someone that you have known all your life. It is a reminder that someone is looking out for you and not to take them for granted. The term brother can also be used in a more spiritual sense and could represent someone you have great respect for. Alternatively the dream can become more negative if you consider the negative connotations of big brother watching you, perhaps someone though well intentioned is smothering you with their support and you feel like you cannot relax.

To dream about your brother-in-law indicates a struggle to find a balance between your characteristics and his. Consider whether you have open conflict with your brother-in-law in your waking life, and if so, whether this is something you need to learn to resolve somehow. Feelings of jealousy or rejection may be causing a distance to form between you and this is something you can work on.
If your brother-in-law is injured in some way, this can show that you feel he is hindering your progress and generally being unhelpful.

If your brother-in-law is dressed up in a suit or formal attire, this can show that you are underestimating his potential and that he is capable of more than you think.