Thank you for your question
My name is Clare
I shall do my best to help you but I need some further information first.
How old is your mother and what are her feelings about this?
Does your mother still have mental capacity?
If your mother still has mental capacity then sadly there is a limit to the actions that you can take other than to have a heart to heart with your brother about his behaviour.
The other alternative is to discuss matters with your mother first, prepare a budget based on the bills and then arrange a discussion between all three of you
I am sorry I know that this is not what you wished to hear but sadly it is the position that you are in
Then take her out for the day, talk to her about it and help her do a budget - then ask if she wants you to deal with it for her
Better still talk to her about giving you Power of Attorney so that you have the power to deal with it
You are most welcome I hope all goes well