Animal Crossing: City Folk Error 80430

My siblings and I have recently discovered that we can use Wiimmfi to visit each other's Animal Crossing: City Folk towns. For some odd reason though, my sister can visit my own or my brother's town, but neither my brother nor I can visit any other town whatsoever! Whenever we try to visit anyone else's town, we receive Error 80430, but I'm almost positive we've entered each other's friend codes correctly. Can someone please help?

Just something to try, and i'm not sure if it would work, but do all the consoles have an account on the Wiimmfi website (wiimmfi.de)? that may help.

It means the friend code you entered for your sister was wrong! Lol re check and try again then it should work :)