Is there any way to allow family members that have been added to each others friends lists via the true friend code for them to have access to their castles etc? I know that brothers and sisters have rooms in one castle but I would like my niece to be allowed into my castle whenever she is on and I am not. We share the same account so I am not on when she plays.
The only way to enter someone's Castle is to teleport to the individual*. If they are not online, you cannot teleport to them, I'm afraid.
If you would like to play at the same time as your niece, we do offer the ability to transfer your characters to your own account - then you can play together rather than having to take turns. It doesn't solve her being able to enter your house when you're not online, but it does open up much more interactive play between the two of you.
Please see this post about transferring characters to a new account. There are a few requirements but our support team can help you with those.
*yes if the owner of the house is offline, as long as someone on your friends list is in the house, you can teleport in ,but I doubt you want to make a separate account that just stands around in a house waiting for you to teleport to them.