Your siblings can sponsor your mother if they meet the financial requirements. They cannot sponsor you. You are too old to be included in your mother's application as a dependent.
No - your mother cannot sponsor you once she becomes a PR.
If you wish to become a PR, you will have to qualify and immigrate on your own. Information about Canada's immigration programs can be found here:
http://www.cic.gc.ca/english/immigrate/index.asp