Dreams involving significant others can often reflect deeper emotions or concerns within your relationship. In this case, kissing your wife and then seeing her transform into her brother's face may indicate feelings related to familial connections, identity, or even unresolved issues regarding your relationship with her family.

The transformation could symbolize feelings of closeness to her family or possibly concerns about how her family influences your relationship. It might also suggest you are processing feelings of intimacy and the complexities that come with it, including how family dynamics affect your partnership.

Consider reflecting on your current feelings towards your wife and her family. Are there any unresolved issues or emotions? This dream could be prompting you to explore those feelings further. Open communication with your wife about your relationship and family dynamics might also be beneficial.