I stutter, my little sibling stutters, my uncle (moms brother) stutters, my great uncle (my grandma’s brother on my moms side)….I currently am in graduate school for SLP. There are current peer review research articles that discuss the genetic component of stuttering. Here’s a good article, published fairly recently in 2017 definitely check it out, https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5370225/