Nikola Tesla's older brother who died in a riding accident was Dane. Dane was Tesla’s older brother and died in a horse-riding accident when Nikola was still a young child, around six or seven years old according to the standard biographical account.
The tragedy became an important part of Tesla family history. Later accounts describe Dane as exceptionally bright, and the death had a lasting emotional effect on Nikola. Tesla was the fourth of five children, with three sisters—Milka, Angelina, and Marica—and Dane as his only older brother.
The accident is sometimes described broadly as a riding accident and sometimes as a horse-riding accident. Those descriptions refer to the same event; the important identification is Dane, not one of Tesla’s later colleagues or relatives.
Dane’s death is also easy to confuse with other dramatic episodes in Tesla’s childhood, including his severe bout of cholera after high school. That illness nearly killed Nikola, but it was unrelated to the accident that killed his brother.