but B2 is not showing that value or not reciving it
Does the RX light on the XBee shield/adapter board flash when B2 should be receiving serial data?
Does the RX light on the Arduino flash when B2 should be receiving data?
I'd put some more Serial.print() and/or Serial.println() statements in the code on the B2 Arduino to see what it is receiving. They will confuse the B1 Arduino, but at least you can get a handle on whether the B2 receives anything.