You can apply for a China L tourist visa with the following documents:
(I) Original passport with validity more than six months and minimum 2 blank visa pages;
(II) Photocopy of the first 2 pages (personal information) of the passport and the recent Chinese visa page if there is any;
(II) One fully completed visa application form in Chinese or English, attached with one of the applicant's recent color photograph (30mm X 40mm)
(III) Certificate of the relationship between you and the person in China you want to visit (original and photocopy)
(IV) Invitation letter from your relative you want to visit
(V) ID card copy or passport copy of your inviter
(VI) Copy of Chinese visa page of your inviter's passport
Sorry that your brother can't apply for the visa for you on your behalf, for the China Embassy in Pakistan don't accept individual visa application actually.
So you should first contact a qualified travel agency of China and settled down all the details of the tour. And then the tourist agency may arrange a visa notice form for a travel group (more than 5 people) and a group-visa for you.