Before you plan to take legal action agaisnt your siblings, you should realise what you have done to take care of your old aged mother and towards her age related ailments.
Your mother can approach the senior citizens welfare tribunal for maintenance alone and she cannot force the unwilling children to be with her always.
Your mother with frail health cannot approach the court or tribunal on her own, she needs someone to support her to file any case or even to get out of the house for all her needs.
There is law to come to her rescue under the said circumstances including the law what you have referred to herein above.
However your mother has one more child besides her two children, in that situation, she may have to implead you also seeking relief against you too along with her other children, what can you do then, can you deny to take care of her owing to the practical infeasibility conditions you face.
The court may ask you that why you have not taken steps to take care of her at least by arranging some domestic help or servant maid to help her at house?
Or do you have anyone to support her to file the said cases against your siblings?
Under section 5 of the act:
5 Application for maintenance.
(1) An application for maintenance under section 4, may be made
(a) by a senior citizen or a parent, as the case may be; or
(b) if he is incapable, by any other person or organisation authorised by him; or
(c) the Tribunal may take cognizance suo motu.
An application filed for the monthly allowance for the maintenance and expenses for proceeding shall be disposed of within ninety days from the date of the service of notice of the application to such person: Provided that the Tribunal may extend the said period, once for a maximum period of thirty days in exceptional circumstances for reasons to be recorded in writing.
An application for maintenance may be filed against one or more persons: Provided that such children or relative may implead the other person liable to maintain parent in the application for maintenance.
Where the children or relative is residing out of India, the summons shall be served by the Tribunal through such authority, as the Central Government may by notification, specify in this behalf.