A way to merge accounts?

You cannot merge two different accounts and Apple IDs. What you can do is to set up your computer for two different users. See the following:

Using More than One iDevice on the Same Computer

This applies mainly to couples who are adding another device and do not want their email, messages, etc. being duplicated on both devices. To begin read: How to use multiple iPhone, iPad, or iPod devices with one computer. You need to establish a separate Apple ID and password for whomever will use the new iDevice. See Apple - My Apple ID and Frequently asked questions about Apple ID. The easiest way is to do this on the computer using iTunes: iTunes- How to set up an Apple ID within iTunes.

On the computer create a new user account for the person with the new iDevice. This will be the user account that person will always use. He/She will no longer use the other user account. This way that person will have a separate iTunes Library

Start by transferring the new device(s) to a new account along with all your data. Save any photo stream photos that you want to keep to your camera roll (unless they are already in the camera roll) by opening your Photos app, tap on Albums icon at the bottom. Now, tap on My Photo Stream album; tap Select; tap on the photos you want to select;, tap the share icon (box with upward facing arrow) in the lower left corner; then tap Save to Camera Roll.

If you are syncing notes with iCloud that you want to keep then you need to open each of your notes and email them to yourself. Later you can copy and paste the text into new notes created in your new account.

Tap on Settings > iCloud > Delete Account (only deletes it from this device, not from iCloud; the person keeping the current account will not be affected,) provide the password to turn off Find My Phone and choose Keep on My iDevice when prompted. Sign in with a different Apple ID to create your new account. Choose Merge to upload your data.

Once you are on separate accounts, you can each go to icloud.com and delete the other person's data from your account.

Note: The essence of the above was created by user, randers4. I

have made substantial changes to improve readability and syntax.

It is possible to share music locally using Home Sharing. Yosemite, the new version of OS X, will introduce Family Sharing. These will enable the two of you to access each other's music.

You have to use two user accounts and only download what belongs in each account, then you don't run into any problems. The use of the new account is the first thing described in the material I posted. You can only have on iTunes Library per device and per Apple ID. You sync to your account while your wife/hubby syncs with the other account. You each have your own separate iTunes Library associated with each or your Apple IDs, respectively.

You will find this will work but you have to follow the directions. If you say you tried it and it didn't work, then you did it wrong.

One of the accounts should be configured for use with your device and Apple ID. The other user account is configured for your spouse's Apple ID. You can only sync your device with your Apple ID in your user account. Your spouse's device is only synced with her Apple ID in her account.

You cannot sync your spouses device in your user account or vice-versa. There is one authorization for the computer, but there will be two devices associated with the computer. You cannot transfer any authorization since there is only one. It would greatly help matters if you would read what was posted including the associated links. They have been used by many others trying to use two iPhones on the same computer without having each person's stuff mixed up with the other person's stuff.