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I'm sorry to hear about your situation. Assuming that your mother doesn't have a will in place, the property that is still owned at the time of her death is considered part of her estate, and the estate is going to be distributed in accordance with the laws of "intestate administration". When you and your siblings are the closest relatives, you'll be splitting that equally (again, assuming that she doesn't have a will in place). The good thing is that you can argue mismanagement and misappropriation of her funds prior to her death by sibling 1 (and sibling 2, if sibling 2 also has been mismangaging those funds). Now the main issue with that is that you'd need to file a case as the administrator of the estate against the siblings that mismanaged and misappropriated those funds, which would mean that you would need to become the administrator upon her death.
Now as a practical matter, you don't have to wait until her death. You can be appointed the legal guardian of her estate during her lifetime, at which point you can take control of her assets and decisions regarding her physical health. I know that this might not be an option given where you may or may not be in your life, but that is a possibility. If that's something that you would want to pursue, you'd need to contact an attorney in your area that deals with elder care / guardianship law.
Hope that clears things up a bit. If you have any other questions, please let me know. If not, and you have not yet, please rate my answer AND press the "submit" button, if applicable. Please note that I don't get any credit for the time and effort that I spent on this answer unless and until you rate it positively (3 or more stars). Thank you, ***** ***** luck to you!