All members of your organization have owner-level access to any projects under the Organization’s account.
If you have an Organization account with username your_org; it has members Jane, Chris, and Rae.
That means Jane, Chris, and Rae will all have owner-level access to any the projects in your_org, for example, your_org/quick-start and your_org/project1.
The members cannot change the organization’s membership; only you can do that.
If you add an organization as a collaborator to one of your projects, all members of the organization will be granted collaborator-level access.