What TV do you use, it may have this built in. Apart from that you have two options.
Either an Audio splitter + BT dongle
Or
Connect the headphones to an AirPlay dongle, that way it becomes AirPlay instead of BT and can be shared natively via the ATV
What TV do you use, it may have this built in. Apart from that you have two options. Either an Audio splitter + BT dongle Or Connect the headphones to an AirPlay dongle, that way it becomes AirPlay instead of BT and can be shared natively via the ATV