The fact that your parents are visiting on a supervisa and that your brother claimed asylum could raise concerns that your brother is trying to move to Canada because the rest of his family is visiting and labs permanent status in Canada. He will need strong proof that his life is at risk not that he just wants to move to Canada to join his family. Would add that parents PR in Canada is not guaranteed so they may need to return home even if your brother is able to secure protected person status.
