There is no family stream under the Ontario provincial program.
The official name of the nanny program is live-in caregiver program. You can read about it at http://www.cic.gc.ca/english/work/caregiver/index.asp It is not considered a skilled profession but because of shortage of live-in caregivers, it's a special program. She would either have to get work experience as a nanny for 1 year or take a 6 month nanny course to qualify. She would also need to speak English or French. This could be a long term project for you and her.
When she qualifies, your brother would have to apply for a labour market opinion for her, see http://www.hrsdc.gc.ca/eng/workplaceskills/foreign_workers/supperimm.shtml and make an employment contract, offer minimum wage etc. If you get the labour market opinion, she can apply for a work permit. The embassy would need to believe that she will return to her home country at the end of her visa which can sometimes be hard to prove, for some embassies harder than others. Once in Canada, she will have the option to apply for permanent residency after 2 years of work. Your brother would, like any employer have to give her pay-slips, withhold her taxes and EI contributions etc. etc.