Have POA for Mom who asked me to buy a house with proceeds from sale of her house. Should I tell my siblings?

She's been living w/me in a rental house for over a year but wants the permanence of owning a house. Wants to be able to paint a room if she wants to (her words!) She wanted me to just pay cash but I did not want to use the majority of the funds that will be for her long term care when I can't take care of her at our home anymore. So I put a good amount down that left me with a mtg payment $500 lower than the rental house. In the rental she paid about half the bills but now I can pay the mtg & upkeep myself leaving her to only chip in for utilities & her 24/7 oxygen. Not sure how my brothers will react. She has age related memory problems but is still what her attorney considers "of sound mind". Because I have better credit than she does, the mortgage is in my name.