Unable to pair two iPhone's via Bluetooth
iOS uses Bluetooth in a very particular way. Depending on what you want to achieve, you can use an App or an iOS feature:


For transfering files: iOS allows you to transfer stuff via AirDrop
For internet sharing, use the built in iOS hotspot feature


Typically, iOS pairs only with accessories such as bluetooth headphones or heart rate sensors.

There are other bluetooth features that are managed by iOS and work without user intervention such as continuity or bluetooth beacon detection.