My brother has an OBITalk softphone number and I gave his access to use my auto attendant powered by Google voice. Is it possible that when he makes calls using my auto attendant to display his softphone number instead of my real Google voice number.
If you mean as CallerID on the outgoing Google Voice call, the answer is no. Google Voice always presents its own number as CallerID and it cannot be changed.
You can set up a second google voice number on your Obi and have his Obion use that trunk. His google voice number will show up as the caller id. And you can set your Obi to send the incoming calls to his google voice number to his Obion number instead of ringing your phone.
Thanks for your help. I think I will go with your suggestion.