Is it possible to use same username but different passwords

I am building one website where i have to import existing users from csv file

The fileds are


username---password---email------storeid---storename


Now the problem is there are many users with same username and email but different storeid and password

e,g one person can have many stores


How should i log them in as username is same

Use the email address as the username on the login page.

The email is also same.