You also have to look at sponsor eligibility:
Criteria for Sponsors (includes but is not limited to):
* A Sponsor must complete a Family - Sponsorship Affidavit of Support.
* A Sponsor must be at least 21 years of age or older.
* A Sponsor must be able to provide proof that he or she is the parent, child, brother, sister, aunt, uncle, niece or nephew of the Candidate (by birth or adoption).
* A Sponsor must be a Canadian citizen or permanent resident of Canada and must be able to demonstrate he or she has been a citizen or permanent resident for at least two years.
* A Sponsor must currently be a resident of Alberta, and must be able to demonstrate that he or she has been residing in Alberta for the past two years.
* The Sponsor must be able to demonstrate employment, private pension or other regular source of income for the past 12 months OR a minimum of CAD $15,000 in unencumbered, transferable and available assets (jewellery, cars or other personal assets are not considered) over and above any income received from government transfer payments (e.g. Old Age Security, Canada Pension Plan, etc.).
* A Sponsor must fulfill their sponsorship commitment prior to sponsoring another family member. The sponsorship commitment is defined as two years from the date that the Candidate became a permanent resident of Canada.
* Please note that there can only be one ongoing sponsorship commitment per household at a time. A second sponsorship from a household could only be considered once the initial sponsorship commitment has been fulfilled.
I do not know if sponsoring parents federally will stop one from sponsoring a brother under AINP but the brothers can not be sponsored as a package deal since under immigration law, they are not considered to be a family unit but 3 separate individuals. Therefore, only one brother can be sponsored at a time. Say you sponsor one brother, he becomes PR, then you sponsor another and the first brother who became PR can sponsor the 3rd. Since family stream is slow, it can be a project that takes many years to complete so it's better if the brothers can qualify to immigrate on their own.