Hi JD,
I appreciate importance of the role that your sister and brother have accepted, as well as the stress that comes with caring for your mother. But one should not underestimate the challenges and pressures of long distance caregiving. Have you seen this thread between NatR and SherriT?
I'm sure there are ways you can help your mom by helping your siblings. Are they willing to accept your help from afar? I'm always careful not be the daughter who comes swooping in to "fix" everything without really understanding the "on the ground" situation. But it can be tough. Have you encountered that?