An applicant who has visitor status, when s/he is abroad, is not advised to apply for passport renewal. If a passport applicant must renew his/her passport under unavoidable circumstances then yes, do apply when abroad.
Such applications will take longer as it will be processed by the original passport office in India.
Do remember that your brother must have valid visitor status in Canada while his passport renewal application is being processed. This means you must apply well in advance before his passport expires/his visitor status expires