Yes, Product Owners are considered to be a member of the Scrum Team. See the definitions for “Scrum Team” and “Scrum Development Team” above.
Each Scrum Team should have a single Product Owner responsible for prioritizing work items for the Sprint backlog along with the corresponding acceptance criteria. A Product Owner may be a member of up to 2 Scrum Teams. Conversely, each Scrum Team will have a single Product Owner as their input for what work to work on.
