How to edite more than 3 characters for First and Last Name

Hi all! Help me out please!
"First and Last Name must be greater than 3 and less than 32 characters!" Some people thier first or last name is just 2 characters such as AJ , DK, LE... When they sign up account, system asks for 3 or more characters for first and last name. Does anyone know how to change or edit that to 2 characters??? Thank You All