How can I use two pairs of AirPods Pro with Apple TV 4K at the same time?

On it's own the Apple TV is not capable of doing this. Like the majority of other Bluetooth devices, the apple 4k TV can be paired with multiple devices, however it can only actively output to a single paired device at any given time. With iOS 13.1 there was a feature introduced called audio share that allowed for two pairs of AirPods to be used together simultaneously, but this is limited to the iPhone and iPad devices.

However, there are ways around this if you're willing to spend a $30-50. What you will need is a Bluetooth Audio Transmitter which I have linked an example of down below, although I would recommend finding one with an external power supply over a rechargeable battery like this one has. This is a small device that when plugged in allows you to connect more than one Bluetooth device to it at a time. Your TV needs to have a audio output port, where you'll plug the transmitter into, as the apple TV 4K (released in 2017) does not have the USB-C port on the back like Apple TV 4th gen (released in 2015) had and transmitters that use this over the standard audio output cost more.

If you're TV does not have the audio output on it you'll need some sort of audio amp or processor that can take an HDMI feed and has Bluetooth built-in.

Bluetooth Audio Transmitter: https://aluratek.com/universal-bluetooth-audio-transmitter-bluetooth-five