Maybe your family have bad communication skills which cause you to stutter more around them. Speaking is a two way street. If your family is large it can be very hard to get a word in edgeways putting pressure on you to speak at a certain time and speak quickly. Getting interrupted a lot can really hurt too. (if you do get interrupted just take a big breath and don't try to talk over them) It could also be how you feel around your family, maybe because you can feel and know they are judging you. I would stutter quite a lot around my brother and sister because I wasn't comfortable around them. ​ So to actually answer your question, you could explain to your family how their actions are affecting you and your stutter kinda like I have done above.