Part of the family

Me and my SO have been married for awhile now, and have a 2 year old. I love his family, his brother and sister act just like my brothers at home ( they're comfortable around me)I moved from N.Y. to Arkansas and I've lived with his father for 2 years and I've been out with his mother quite a bit.. but whenever they introduce me they still say " --- , this is Danielle, my son's girlfriend. " that drives me nuts! Anyone else stuck here? How long did it take to be part of the family? Do they EVER call you daughter in law / sister in law?