How can I give my wife emergency access to logins, passwords, etc.?

There are a number of suggestions provided in Jeff Moser's post related to this.

A Proposed Solution

Let’s borrow an ancient yet incredibly useful idea: if it’s really important to get your facts right about something, be sure to have at least two or three witnesses. This is especially true concerning matters of life and death but it also comes up when protecting really valuable things.

By the 20th century, this “two-man rule” was implemented in hardware to protect nuclear missiles from being launched by a lone rogue person without proper authorization. The main vault at Fort Knox is locked by multiple combinations such that no single person is entrusted with all of them. On the Internet, the master key for protecting the new secure domain name system (DNSSEC) is split between among 7 people from 6 different countries such that at least 5 people are needed to reconstruct it in the event of an Internet catastrophe.

If this idea is good enough for protecting nuclear weapons, the Fort Knox vault, and one of the most critical security aspects on the Internet, it’s probably good enough for your password list. Besides, it can make a somewhat uncomfortable process a little more fun.

Let’s start with a simple example. Let’s say that your master password is “[email protected]”. You could just write it out on a piece of paper and then use scissors to cut it up. This would work if you wanted to split it among 2 people, but it has some notable downsides:

It doesn’t work if you want redundancy (i.e. any 2 of 3 people being able to reconstruct it) Each piece would tell you something about the password and thus has value on its own. Ideally, we’d like the pieces to be worthless unless a threshold of people came together. It doesn’t really work for more complicated scenarios like requiring 5 of 7 people. Fortunately, some clever math can fix these issues and give you this ability for free. I created a program called SecretSplitter to automate all of this to hopefully make the whole process painless.

Here's the link to the SecretSplitter software he created.

You might also be interested in the Dead Man's Switch website.

You never know when you might be hit by a bus. Are you prepared for it? Maybe you want to pass on important information, notify some online acquaintances or apologize to an old friend. Enter DeadMansSwitch.org.

The service is simple. Type an email and optionally attach a few files. Every few days we will send you an email with a link that verifies you are still alive. If something does happen we will send your emails 30 days after we last heard from you. Is 30 days too long? No problem, someone close to you can use an emergency release code to dispatch the emails early.

Your emails and files are encrypted on the server using AES-256 encryption to help protect your data.

We have actually covered this in some detail already on Security SE

• Storing account credentials for spouse/loved one?
• How to prepare for protecting identity after death?
• How to secure identity after someone dies?
• Is there a digital “safety deposit box” equivalent?

These posts go into detail about what you can and can't share - there may be some legal/contractual ramifications if you share logins for banking etc.

So there are some simple technical solutions (Keepass/DropBox etc) and some procedural ones (password for your master password file stored in an envelope with a solicitor or notary)

This may sound harsh, but while you may trust your brother - it is often best to avoid placing them in a position where they have the opportunity to do something malicious, as his circumstances may change in such a way that forces him to. (as an example - gets accidentally in debt to someone with organised crime links - who blackmails him into payment on threat of injury to family) - much better to trust a lawyer, who has a professional and ethical code of conduct which will (hopefully) act as an additional barrier to misconduct.

The most straightforward way ? Export all urls with the corresponding passwords, together with a short manual where applicable, to print them out and pass to your wife.
If what you said (adopting your ways of digital security not being an option), I can't see any other, more practical way of handing that stuff over.

Either put the printouts in a safe, or integrate them in your will. Obviously, putting those virtual things on paper presents you with a huge security risk.

Edit: updated my answer for future references. As suggested in the comments, there is a possibility to bypass the security risk mentioned above, by using LastPass's one-time password (OTP) service. This way, you only have to keep a single-use master password on file.