When I first started using Apple Music I signed up for a solo subscription. During the day, I would listen to music on my Mac, and my family would listen to music on the iPad. If we listened at the same time, we would get the error:
“Looks like you’re listening to music on another device.”
Eventually this error became too annoying and I looked at upgrading to a Family subscription. The Apple Music Family subscription allows up to six people that are part of the same Family Sharing group to play music at the same time.
It sounded like this was probably what I needed, but in all of the documentation I read, it wasn’t clear whether two devices that were logged into the same Apple ID would be able to play music at the same time. I talked with Apple’s support team and it still was unclear so I went ahead and upgraded to try it for myself.
After upgrading I tested playing on multiple devices, and it worked fine. If you have an Apple Music Family subscription, you’re able to play on multiple devices that are logged into the same Apple ID.
Update: More context from Benjamin Mayo on Reddit:
If you have the Apple Music family plan, multiple concurrent device streams increases to 6 rather than 1. HomePod and Apple TV usage do not count toward this limit.