Gabriel Bethlen’s ancestors, the Neczpáli family, owned estates in the counties of Békés and Zaránd. It is believed that the Bethlen family took its name from the village of Iktár in Temes County, which they likely acquired in the 14th century. Gabriel Bethlen’s grandfather, who bore the same name, led six hundred lancers at the Battle of Mohács and, following the defeat and internal conflicts, supported John Zápolya against Ferdinand. His father, Farkas Bethlen, initially a supporter of Ferdinand, distinguished himself in battles against the Turks, then, at the call of John Sigismund, settled in Transylvania, where he became the country’s chief captain. He took part alongside Stephen Báthory, Prince of Transylvania, in the Battle of Kerelőszentpál in 1575, and for his merits received the Marosillye estate in 1576.

Gabriel Bethlen’s mother, Druzsina Lázár, came from a family of Szekler nobility from Gyergyószárhegy. Of the children of Farkas Bethlen and Druzsina Lázár, only Gabriel and his brother István — born in 1584 and later a prince — reached adulthood. The two boys were raised in the Marosillye castle until their father’s death, which occurred in either 1590 or 1592. Although they learned to read and write at home, their upbringing emphasized practical and military skills. Farkas Bethlen had intended to send Gabriel to study at the Jesuit Academy in Cluj, but his premature death prevented this.

After Stephen Báthory confiscated the Marosillye estate from the orphans, their mother moved with her sons to her brother, András Lázár, in Gyergyószárhegy. Following their mother’s death, the boys were raised by András Lázár, who prepared them for a military career and paid little attention to their cultural education. Gabriel Bethlen later recalled that they had not been taught Latin, a skill he managed to acquire partially on his own.