Re: at what stage will he introduce me to his family?
dating or courtship acceptance varies by family so there is no one practice. Now yor words are interesting that he does not want to introduce you to his family or it may be filtered back to his parents..? what is his family. Is it uncles and aunts and cousins etc, if so, it makes complete sense, why would he want them in his business? I did not have anyone from my extended family meet my wife until after I had personally told my parents.
He may be trying to determine if you are the one for him, or he may not be serious. The info you have provided does not give enough info to give any insights 