When I use TOR, is there any way that the family could see I use it?
Yes, in almost all cases. In general WPA use PSK, which means anyone with the password case decrypt and sniff packets. If this is a concern there is one exception, and that is WPA-Enterprise. From http://www.ciscopress.com/articles/article.asp?p=1576225
Users never deal with the actual encryption keys. They are securely created and assigned per user session in the background after a user presents their login credentials. This prevents people from recovering the network key from computers.
So this means that each computer uses a unique key for their wireless encryption so another computer with access cannot sniff someone else's wireless connection.