You can connect two pairs of AirPods to the same iPhone, which is a great feature especially during travel when you and your travel companion want to watch or listen to the same thing. You will need iOS 13+ to do this.
To set this up:
Open the charging case lid and hold the pairing button on the back of your second set of AirPods until the inside light flashes.
Bring it close to the iPhone for pairing.
Tap the pop-up menu confirming you want to pair the AirPods to your iPhone.
Start playing music, etc.
You’ll hear sound through the AirPods you just paired.
Now tap the AirPlay button.
Choose the first pair of AirPods you connected.
Sound should now be heard in both sets of AirPods at the same time.