Do auto insurance rates increase if you add an additional driver who is not a relative?

yes,it's insurance rate increase. but it depends on certain factors,

i think you should have to talk with insurance agent or company prior to including someone to your car insurance, untill it is really necessary, you will not put a new young driver who has low driving record for a insurance coverage, it might depart a long term tag against your insurance cost,insurance rate also depend on age of person,driving record of his,,may be also depend on gender ,