Why do shared reminders not push to both iPhones?

When working with the native Reminders app in Yosemite 10.10.3, I am able to create shared reminders in which I can collaborate with someone and add and complete reminders, I notice that the reminders that I create push to my phone when told to; however, the other user does not get a push notification on THEIR phone. They do get the reminder pushed to their MacBook but not the phone, making the Reminders app much less useful for me. Anyone have a solution? Both phones are using the very latest versions of iOS and OS X.