No, one orb will get every person in your party in. However, if you want to do the BCNM for each person, then you'll need each person to have an orb. After you do the BCNM, the orb will still be in your inventory, but will no longer work. I'm pretty sure I heard you can trade the orb back to Shami in Port Jeuno for a nominal amout of Jeuno fame.
Orbs are obtained the same way. You talk to some guy in jeuno that wants beastman seals and he gives you an orb for a certain ammount of beastman seals you give. I hope that helps you!