How to pair two iPhones for call forwarding?

SKBhatia wrote:

to use one hand set to receive calls incoming on the other phone though having different phone number.

You can set up call forwarding from one phone to the other phone, but you can't pair them to do what you want.

See this --> Set up call forwarding on iPhone - Apple Support

What you are attempting to accomplish only works when both iPhones are set up and using the same Apple ID. Both iPhones must be connected to the same Wi-Fi Network and Wi-Fi Calling must be activated (feature provided by the carrier) along with Allow calls on other devices set to ON.

This feature works well between an iPhone and a Mac or an iPad. This feature is limited when it comes to two iPhones because of the connection to the same Wi-Fi Network limitation.

Axel F.

You can also setup call forwarding through your network provider (if its supported).

go to settings > apps > phone > call forwarding > toggle the switch and put in the other number

note that this is a network supported feature and you might need to check with your network provider for support and or charges if any.

Pair them to do what exactly? In the traditional sense iPhones don't pair with each other. Perhaps you can provide more information on what you hope to accomplish.