Can more than 1 sibling serve as Power Of Attorney?

I have been serving as primary caretaker for my 87 year old mother - ensuring she has a working care network to facilitate her safety, health and well-being in her own home - her wish. Over the past 15-20 years I have provided financial support to pay her bills, coordinate her medical care and have arranged for meals on wheels, prepare meals in advance, and have a nurse come in weekly. My aunt, sister, my husband & I rotate to stay with my mom so she has 24 hr support as she needs. I take leave from work to do this. My brother lives about 10 mins away and cannot or will not take care of critical matters, and visits infrequently, and cannot or will not participate in sharing this responsibility. He cuts grass and fixes some items and charges my mother for these visits. He makes no attempt to provide help for day to day care to provide us with respit, Let alone act on her behalf as POA. At each phase, I had to step in to act on her behalf or she would've been in a serious medical crisis. He does not monitor when my mother needs critical assistance and has no clue of her day to day condition let alone sense of urgency to take care of her. As she continues to become more dependent than she already is, I'm concerned that I will not be able to act to help her.