With Movies Anywhere, you can watch most of those digital movies across all of your connected accounts. Well, at least all of the ones connected to supported services, which currently are Google Play, iTunes, Amazon, and Vudu. Here’s everything you need to know about Movies Anywhere.
I don’t have this problem because I only purchase content from iTunes, but I know a lot of people that do have multiple accounts. Lory Gil did a nice article explaining how Movies Anywhere works.