If you have different Apple IDs on those two devices, then this is possible.
- Add and Join with another device as Group calls after inviting
- Leave the original call.
Add another person to a call
Any participant can add another person at any time during a Group FaceTime call.
- During a FaceTime call, tap the screen to open the controls, swipe up from the top of the controls, then tap Add Person.
- Type the name, Apple ID, or phone number of the person you want to add in the entry field at the top.
- Or tap
to add someone from Contacts. - Tap Add Person to FaceTime.
Join a Group FaceTime call
When someone invites you to join a Group FaceTime call, you see the incoming call. If you decline the call, you receive a notification that you can tap to join the call at any time while it’s active.
Leave a Group FaceTime call
- To leave a group call at any time, tap
.
The call remains active if two or more participants remain.