It happens a lot. Mothers can treat their sons like fine gold and their daughters like dirt. It is probably the old system where men were held in higher esteem. Plus, if you treated a man the way some women are treated, they would go away and never come back. Maybe women should take a lesson from men. If someone doesn't treat us well, we should just walk away. (Wish it were that easy)
CamCam, we need more information. You mention your Mom has memory issues, how long has she had this medical condition? What is she able or unable to do for herself? You see her daily, but how often does your brother see her. What type of caregiving does he do?
Sorry that Mom isn't being sweet and compliant for you. Welcome to the club.