Several factors can contribute to stuttering. Kids Health from Nemours stated that about 60 percent of people who stutter also have someone in their family who stutters.
The stuttering may result from abnormalities in the brain, specifically in the language regions, which are passed down through families. Some children stutter because developmentally, their language and speech skills cannot keep up with what they would like to say, thus resulting in a stutter.
Some people may stutter after sustaining an injury to the head, such as with a traumatic brain injury, while others may develop a stutter after emotional trauma, though the MayoClinic.com noted that it is an uncommon cause of stuttering.
Complications can arise from stuttering in children. For example, the MayoClinic.com noted that some children may develop social anxiety disorder, in which they may be afraid to speak in front of other people. Some children may be bullied.
https://www.empowher.com/stuttering/content/about-stuttering-children