It is not possible to receive a Mobile Push authentication request on two phones simultaneously during a single sign-in attempt. Allowing such a feature would be a considerable security risk.
Nevertheless, you can enroll more than one phone and use them interchangeably during separate sign-in attempts.
How to Select Phone to Receive Mobile Push?
Rublon sends the push notification to the mobile device you select in the Phone dropdown on the Rublon Prompt during each sign-in attempt.
How to Change Default Phone?
If you have enrolled more than one phone, one of them will always be selected as default. You can change which phone is chosen as default on the Manage Authenticators view:
What If I Use Auto Push / Promptless Application?
You can only select the phone to receive Mobile Push when you log in to an application that supports the Rublon Prompt.
If the application does not support the Rublon Prompt or Auto Push is enabled, Rublon always sends the push notification to the device that was added or used last time.
If you have two applications and one of them supports the Rublon Prompt, you can log in to the one that does, select the default phone and then log in to the one that does not. You will receive a Mobile Push on the mobile device you selected.
Rublon Prompt - Rublon User Guide