But they could each setup call forwarding to each other’s exchanged phone numbers so they would receive the right phone calls.
Edit: No, wait, hold on. That sounds like I just created an infinite loop.
Call to A gets forwarded to B which is set to forward it to A which will forward it to B which then forwards it to A…
I only have 2 phone numbers, so I can’t test it.
I fixed it for you (click it, seriously):