Yitzchok Sternhartz (1808–1871) was the second eldest son of Rabbi Nathan of Breslov (also known as "Reb Noson"). He was born in the town of Nemyriv, Ukraine (located nine miles (14 km) northwest of Bratslav), where his father had become a close disciple of Rebbe Nachman of Breslov. Sternhartz remained close to his father all his life, and was the inspiration for his father's substantial written correspondence during the last 15 years of Reb Noson's life.
Read more about Yitzchok Sternhartz: Biography, Aliyah To The Holy Land