Normally, a person cannot sponsor his brothers or sisters, or other relatives. However, in some cases a person can sponsor a brother or a sister, niece, nephew o even his own grandchildren:
If parents are deceased
the person to be sponsored is under 18 years of age
There are some requirements for both the sponsor and applicant:
The sponsor needs to sign a guardianship agreement with the Canadian Immigration Office
The applicant needs to collect consent from the home country
Other than the orphan family member, one can sponsor another relative:
If a Canadian citizen or permanent resident has no spouse, common-law partner, conjugal partner, children, parents, grandparents, aunts o uncles in Canada and do not have any family members outside Canada, s/he can sponsor a relative connected by blood or adoption, regardless of age.