Remember to add aditionals people they dont make any money, there is not extra charges for wife and kids, no matter how many kids do you have under the monthly payment will be the same as if you were alone in your insurance when is coming from yourwork place, so If you tell them my boyfriend (Novio) for sure they will tell you not you can not, and its true you can not, But if you tell them mi marido but we are not married, they will give you the correct answers how he can add you.
But yes as somebody else said here he must go to the Human Resource Department from at his workplace and they help him with not stress.