Normally you can not sponsor your brother, at least not in Ontario. If you sponsor your parents and your brother is under 18, he may come with them as their dependent but you have to have good income to take responsibility for 3 people. According to table 4 on here:
http://www.cic.gc.ca/english/information/applications/guides/5196E10.asp if you are yourself single, you need to make at least $40,259 per year to sponsor 3 more people. I do not know how long you need to be off welfare.