If you poke around here and finds the posts about drugs, You will find they are inconsistent, anecdotal, and sometimes placebo. Why we stutter? I dont know, but I can relate to the situational stuttering. It sounds like you have a desire to be more fluent in some situations and have negative emotions connected to others (like your family). That's going to set off our fight or flight response. Humans have evolved much faster technologically and culturally than our bodies can keep up with. So now, a lot of time, our brains and bodies are overreacting to things that scare us, but won't necessarily kill us. Take a look at somatic therapy. It talks about reprogramming how our bodies react to situations and we replace those responses with more positive ones.