Hi Robert,
Yes, according to the PMBOK6 (Section 13.1 Identify Stakeholders), project team members are considered stakeholders because “a stakeholder is an individual, group, or organization that may affect, be affected by, or perceive itself to be affected by a decision, activity, or outcome of a project.”
So, if a new team member joins, you should update the stakeholder register, not necessarily because their influence is high, but to ensure their interests, communication needs, and engagement levels are properly identified and managed.
Hope this helps.
Elena