How can three people negotiate against one person?

Not sure of the question but i think you are referring to negotiation dynamics. In any negotiations there should be a equal number of respesentative from each team. I like to keep these as a minimum eg 2 on 2 and i like to keep lawyers out of the discussion. I try to manage the atmosphere and keep people focused on the issue and not get distracted and go off on tangents. In relation to negotiation dynamics the team that has the most members has the advantage. If your team arrives with more people than agreed you need to deal with this before the meeting starts as the dynamics of the meeting will be compromised.