Obeying one's parents in matters of nikaah

I have been engaged for almost 1 year and me and him want to get married so there will be no more haram. His family is okay with it but my parents don't let me marry him just because he is Arab and I am Turkish. They have no Islamic reason and they don't want to pray and know nothing about Islam so it is not normal for them to marry at this age. So I heard if the father doesn't have Islamic reason then it passes to my brother to be my witness and then passes to uncle and if they both don't agree then an imam can be my witness is it true? And I also heard a man's parents don't need to know about the marriage only women's parents. I know no one of my family would agree because they aren't aware with anything about Islam and they don't find it normal so I was wondering can the imam from the mosque be my witness since my family don't have any Islamic reason, and my parents don't know about the marriage?