As someone who grew up a significant stutter that has become a mild one thanks to speech therapy, I recommend talking to them about therapy. My parents were supportive and I'm very grateful for that. If it's bothering you, nothing bad is going to happen if you bring up the question. Your parents may not talk about it because they think you might not want to do it, or they just don't understand your feelings about it. I really enjoyed learning about the all the different kind of speech disabilities, and the techniques to deal with them.