How to Sync 2 iPhones together?

Me and the girlfriend both have iPhones (me an iPhone 5 and her an iPhone 4s) we both have Apple ID's and both download music. Is there anyway we can link the accounts together so when I download music she gets it aswel and vise versia

IOS devices are synced to iTunes, not to each other. Apple designed it that way to prevent you from doing… What you want to do. Apple designed their iPhones that way because they also sell the media that goes on them. Rather than sync phones together or to the same iTunes why not simply try copying them from your computer to hers using a flash drive - she can then import them into her own iTunes as if they were her own songs.

Well copying music and apps would obviously be copyright violations, you can't do that.

The only way is to put them both on the same iTunes account.

The only way would be for both of you to have the same itunes account. It won't work otherwise, as it's copyright infringement.

How doI sync my phone to my husbands