Honestly sometimes your family is able to see outside the box. When people are involved in a relationship, you can't always see whats right infront of you.
If your family is against who you are with, ask them to give you the reasons behind their choice. Maybe they have vailds points that you make need to look over and decide.
If they just like them because of something simple then don't worry about it. I mean in the end it's you and that other person who spend the most time together and if your happy with them...then well your family should be happy as well