In principle, an invitation is limited to parents and siblings to allow them participation in your graduation ceremony. Copies of passport, ID, Certificate of Family relationship and Certificate of Employment of the people you seek to invite are required. You may submit these documents to the affiliated department and visit the Office of International Affairs once the documents are forwarded to the Office of International Affairs by the department. The invitation letter issued by school is not required by diplomatic offices for visa issuance. Visas may be issued or denied regardless of the invitation letter.