Is it possible to merge two iTunes Store accounts so we can share apps and other purchases?

My wife and I each have iTunes on our PCs. Originally, I set these up with separate iTunes Store accounts. I was led to believe that we ought to do this because an email address is used for the Apple ID, and we each have one. I'm thinking now that was a mistake?

Here's the problem: Each of us now has an iPad, and we're each buying apps on our own accounts and syncing to our own PCs. Because of these separate accounts and iTunes PCs, I understand we're unable to share our purchases – which, AFAIK, Apple expressly permits on up to 5 associated family devices. (Please correct me if I'm wrong.)

Is it possible to merge or consolidate two different Apple iTunes Store accounts so we can share the apps and other purchases we've made? (We are married, so legally it is community property anyway! :-)

Alternatively, is there a way we could maintain our separate accounts but still sync each others' devices in a way to get both sets of apps on each iPad? We've already made some redundant purchases (and thus wasted some $) and I'd like to avoid that in the future, if possible!

Home sharing should allow you to see each other's libraries over your home network, and drag apps from your wife's onto yours and vice versa. You can definitely do this despite having two accounts - my wife and I have a similar problem. You may have to enter both passwords from time to time to authorize purchases, though.

I found some help setting this up from "Activating Home Sharing in iTunes".

I believe you can also sort hers by "items I don't have" so you can see what she might have bought of interest to you, although I'm not sure you can automatically sync them.

This SuperUser question seems to suggest that merging two accounts is not an option:
Can I merge 2 iTunes Store accounts?

Another suggestion -- you can authorize itunes on your computer to play content from your wife's account ("iTunes -> Store -> Authorize Account") as well as your own.

And you can do the same for itunes on your wife's computer.

This will allow you to play both you and your wife's content on both of your computers. However, this way you will have to duplicate the content on both computers.

The way me and the wife have got around this is to use two accounts but have the same password so we don't have to remember a different password. This way, when you come to update your apps, it doesn't matter which account pops up, it will be the same password.

We also have a third account. Mine, hers and shared. This is because I have had mine for years and so has she. Then when we got married we decided to create joint account so we don't have to worry about potentially buying an app twice and it will also automatically sync between our 2 iPhones and our two iPads. Again, using only one password for 3 accounts. Ultimately, in a few years any older apps wont be required and we'll mainly use the joint account. Also, all three accounts are on the same debit card.

Even as of 2017 it is still not possible to actually merge two accounts, however, since 2014, with the release of iOS 8 and OS X 10.10 Yosemite it is possible to set up Family Sharing.

Family Sharing enables shared usage/download of all members of the family's purchased Music Books & Apps & will also set up a dedicated shared calendar which can optionally be used to notify members of upcoming events etc.

Personal data is not shared, only the 'right' to use apps/music/books previously purchased by any member & henceforth purchased under the family membership.

One account will be designated Family Organiser - and all purchases in future will be charged to the organiser's account - others can be designated as Adult or Child, with parental controls over what data can be used with or without explicit permission from an Adult.