i want to sponsor my brother in pakistan

Considering your situation, I think your brother can apply for an S type.
Firstly, he can prepare the required materials including his passport and its copy, the application form affixed with a passport-style photo taken recently, an invitation letter from your school, an invitation from you, copies of your residence permit and passport, as well as the relationship certificate and his health certificate. And then submit the application to the consulate general of PRC to apply for it.