Maybe it will be more helpful if you told as about your father status in Canada (PR, citizen,...), and the relationship with your mother (married, common-law...). Since we don't have all the info, I will answer your question based on my assumptions.
If your dad is a PR or Canadian citizen, and that he is married to your mom, he can sponsor your mother to come to Canada through spousal sponsorship. There is no minimun income reuired.
As for your brother, given that he is 25years, your dad can sponsor him if:
•is over the age of 22 and has been continuously enrolled as a full-time student and depended substantially on the financial support of a parent since before the age of 22.
You can read more about this at http://www.cic.gc.ca/english/immigrate/sponsor/spouse-apply-who.asp#sponsoring