No. Within a single organisation's Company level Directory tool, each person with a user profile is uniquely identified in that organisation's Procore account by their email address (see Add a User to the Company Directory). Additionally, each person in that organisation's Company level Directory tool can be associated with only one (1) vendor/company record. For example, if your organisation is a main contractor and you have a list of subcontractors that you want to add to your organisation's Procore account (a.k.a., Procore company account), each employee of that subcontractor can only be associated with one (1) vendor/company record in your organisation's Procore company account.
Jack Smith from ABC Concrete is a subcontractor. He performs work with two different main contractors. Each main contractor has their own instance of a Procore company account (i.e., Gold Main Contractors and Silver Main Contractors). Each main contractor must also create a company profile for ABC Concrete and a user profile for Jack Smith in their company's Directory tool. Within each company's Directory tool, Jack can only be associated with one (1) vendor/company record (i.e., ABC Concrete). In this scenario, Jack Smith may use the same email to log into each main contractor's Procore account. However, within each individual main contractor's Procore company account, Jack Smith can only have one (1) email address to use to login to that organization's Procore instance.