I think ideally everytime you work with someone else, its as a team. However, in all teams there is always a team leader.
I have a situation similar to what you describe. I am the higher level assistant and have three other assistants who I work with. We are a team - but I am the team leader and the final decision is mine. When a tough question or situation presents itself, they look to me for guidance and follow my lead. This may sound kind like I'm giving out orders and telling them what to do, and its mostly true
, but I am also the person ultimately responsible when when things go wrong. I have the most experience and knowledge of the four of us, I am the one that the boss comes to and expects answers. Yes, I am the one that gets the talking to first whenever we drop the ball on something
The other assistants knew that this is how this team works before they accepted the job and were more than happy to have someone else be the leader. We used to have two other assistants before who where not so happy with the set-up and it really created a lot of problems for the rest of us. In the end, they decided to either leave the company or change positions and worked out well for all.