marriage is between two families and not two people. This is a big fat truth about marriages in our society. As long as you were ONLY with HIM things were fine now that you are getting to know HIS FAMILY also things are getting different.
If his family is different than yours , then your family must also be different than his. does he ever complain abt your family being different ? I mean he shd also be feeling that. If not then he is being quite and trying to adjust. If he can adjust for your sake then why can't you ?
and dear he is your own choice , its not arranged u will have to compromise on few things. but yes I agree that your inlaws not coming to ur sis wedding was rude.
think alot before getting married , think how much can u adjust and compromise with him and his family , its not just your life that will be affected but his too if God forbid things dont work out.