Authorities have concluded that a 13-year-old Maryland boy who starred in his family's popular YouTube show died of a heart condition that commonly causes cardiac arrest in young people. The Capital of Annapolis quotes the Office of the Chief Medical Examiner in Baltimore as saying that Caleb LeBlanc died Oct. 1 from hypertrophic cardiomyopathy. Caleb starred in his family's online video series called Bratayleys, which has documented the family's daily life since December 2010. The video has a dedicated young fan base with millions of views. On Tuesday, family members posted on Instagram that Caleb's condition was undetected in his regular checkups. According to the American Heart Association, hypertrophic cardiomyopathy affects one out of every 500 people. (More YouTube stories.)