"Do you need me to call our parents over and ask my family to issue a certificate to prove that Zhou Xing is our cousin? Since when did we have to prove our family background, ancestors, and all our family relations when coming to university? Do you have that privilege, or do we have an obligation to do so?"
Was it normal for cousins to spend time together alone? Of course! Nowadays, families had fewer children, so it was normal for children to address their cousins as elder sisters or brothers. The line between cousins and siblings was not so clear-cut anymore.
Even so, they were still relatives!