The year of Theodor-Peter's birth is unknown. He was apparently the eldest son of a wealthy shepherd from the Haemus Mountains, according to Madgearu. On the other hand, no source records that he or his brother, Asen, owned cattle. Madgearu says, they may have administered an imperial horse farm, adding that their estates were most probably located near Tarnovo. Historian Ivan Dujčev writes that the brothers were local chieftains in the Balkan Mountains.