You have only stayed with your mother for few days at a time, whereas your brother has to look after her 7 days a week, which is much more than a full time job. If he is drinking alcohol too much I would think this is a coping mechanism! Perhaps he needs more support and, although you may not want to hear it, this type of care is considerably harder (and soul destroying) than just turning up for a few days. I think your brother is amazing to give her this care, but it could be getting too much for him. Perhaps the "Martyr" feeling is because he is doing all the hard work and, to be honest, it doesn't sound like he is being appreciated!!