Legal Question in Employment Law in Pennsylvania

Yes, unless you can prove that you are being paid less as the result of a discriminatory motive that is prohibitted. Pennsylvania and federal laws prohibit discrimination based on age, race, sex, ethnicity, disability, etc. Therefore, your employer cannot pay you differently on the basis of these protected attributes.

Otherwise, your employer can pay the other individual whatever it wants to. For example, it is technically not illegal to pay the inexperienced child of a family friend more money than you as a favor.