What to do if you have a speech impediment that hinders your relationship with your parents?

I have a speech impediment that hinders my ability to communicate fluently. The issue that I'm having is with my parents as they never seem to want to talk to me and I feel as if they are ashamed of me cause I am not a talkative person. My younger sister, however, who is more fluent than I am, usually gets more of the attention from my parents and whenever I'm around I feel as if I'm not wanted there. I've tried talking to them, but they either tell me to stop worrying about it or they just ignore the problem (and me) altogether.