Can someone else instead of my go to an One to One appointment?

I don't see why not...

The official terms can be found here:

http://www.apple.com/retail/learn/one-to-one/terms.html

Apple does not explicly state that no one else can go in your place, but they do say that membership and services are nontransferable, so that would seem to imply that your father or sister could not go in your place. But call or visit the Apple Store and ask.

Regards.