akamine_chan pointed this out to me, and I want share it.
Fannish Next-of-Kin Policy at AO3
What does "fannish next-of-kin" mean?
The Archive allows you to choose someone to manage your fannish works if you die or are permanently incapacitated.
What does my fannish next-of-kin get to do?
We will transfer control of your archive account to your next-of-kin. After that, they can follow whatever guidelines you set for them. You might ask them to leave all of your fanworks alone but transfer control of any challenges you were running to people of your or their choice. You might ask them to orphan all of your fanworks and close your account.
How do I choose someone?
That's up to you. It should be someone reliable, someone you trust to make decisions about your fanworks.
What do I do once I've chosen someone?
Both you and your fannish next-of-kin need to send a message to otw-abuse@transformativeworks.org indicating that you want to have him/her as your fannish next-of-kin and that s/he agrees. You need to provide your Archive usernames for our records. When we receive matching requests, we will confirm that a fannish next-of-kin arrangement is in place.
If they're my next-of-kin, am I theirs?
The relationship can be reciprocal if you want, but it doesn't have to be. However, you can only have one person as your fannish next-of-kin at a time.
Why can't I have more than one fannish next-of-kin?
We want to know who has the final say. This arrangement exists precisely so that we don't have to mediate disputes over what you would have wanted.
What happens if my fannish next-of-kin also dies?
You would need to choose a new person. Your fannish next-of-kin can also designate someone else as their own fannish next-of-kin. If A designates B as a fannish next-of-kin, then dies, and B designates C as B's fannish next-of-kin, when B dies C can control all the accounts that B controlled, which at that point would include A's.
What if my fannish next-of-kin decides s/he's tired of being my fannish next-of-kin?
Either party can revoke a fannish next-of-kin agreement by sending a message to otw-abuse@transformativeworks.org. We will inform the other party that the agreement has been ended. Please include your username and the username of the other person involved in the agreement so we can find the right record.
When a fan is dead or incapacitated, the fannish next-of-kin will have control of the account and can make any decisions about it, including handing it off to someone else; the Archive cannot control whether or not anyone shares password information with anyone else. If the fannish next-of-kin lets us know that s/he wants to stop managing the account, we will permanently suspend the account, which means that all existing content will stay in place, but nothing may be changed or added.
What if I decide I don't like my fannish next-of-kin agreement?
Send an e-mail saying that you want to terminate the agreement. Please include your username and the username of the other person involved in the agreement so we can find the right record. The Abuse Committee will e-mail the parties involved in the agreement to let them know. Either party in an agreement can terminate it. You are free to choose a new fannish next-of-kin.
What if my fannish next-of-kin does something I wouldn't like?
Please choose someone you trust. It would be difficult or impossible for the Archive to enforce the exact terms of your agreement. All we will do is verify your status and transfer account control to the appropriate person.
How can my fannish next-of-kin get control of my fanworks?
A fannish next-of-kin can activate the agreement by sending a message to otw-abuse@transformativeworks.org that you are dead or permanently incapacitated. The Archive will send a message to the email address associated with your account. If we do not receive a response from that address within ten days, we will transfer control of your account to your fannish next-of-kin. The Archive will not do any independent investigation into whether you are dead or incapacitated.
Why won't the Archive check to see whether I am really dead or incapacitated?
We don't want to be in the position of collecting and possessing personal information of the kind that we'd need to confirm what your fannish next-of-kin says. It is your responsibility to choose someone you trust. If you want a custom arrangement, we suggest you make private arrangements with someone you trust to handle your passwords and accounts in the event of your death or incapacity.
What happens if I die before choosing someone?
Your account will remain just as you left it. No one will be able to delete, orphan, or modify your fanworks except in response to a ToS violation.
Why should I bother choosing someone?
It can be useful to have someone you trust as a fellow fan to make decisions about your account.