I don’t know your age or the circumstances but I am curious as to why your boyfriend’s parents want or need to meet your parents when you aren’t even engaged. I could understand your boyfriend wanting to meet your parents himself, but I’m not sure why his parents need to meet yours at this time. especially since their son hasn’t even met your parents yet.
You could tell your boyfriend’s family that you’ll introduce your parents to them sometime in the future when your relationship has progressed to that point or you could simply explain the situation to them and tell them that your parents are lovely people but they are involved in a very strict religious organization that prohibits dating outside the religion and it would complicate things for you right now if you were to meet them at this point.
Perhaps you could show them a few photos of your family and your self with them so they get the idea and perhaps that will be enough for them for now .