I am not sure what website exact website you want to access, I guess you are talking about fishville where you play the fish games on facebook. Many people use proxy servers to access blocked websites, you can also try it... (click here)
, open the link and then copy or type in the url of the website you want to access and proceed in the "web address" box and click "go" to visit the site and access it's contents. In simpler terms, click the "click here" (above) and in the "web address" box of the new page, type in "www.facebook.com" or "www.fishville.net" etc. etc.. and click "Go" and see if you can proceed with it or not. If it's not successful, there's no option to access it without getting your cousins permission and to let the site unblocked.
If you need further help, let me know.
Thanks for using FixYa.