Marrying your daughter away is one of the most difficult thing for the parents to do. There are too many doubts, insecurities, worries that go along the whole process. So if the parents see they have a good match for their daughter/son within their family they would prefer it because usually one knows their family better than they would be knowing some strangers. So i think there is absolutely nothing wrong with that. However, if you think who they have selected for you is not someone you are compatiable with then let your parents know about that. I am sure they would listen to you. No parent want their kids bad so they would definately understand your point of concern.