We are all "old souls" because we have always existed.

The jiva-souls are eternal spiritual living PERSONS and can never be destroyed, terminated or extinguished, the jiva-souls are indestructible.

Bhagavad Gita As It Is - “Never was there a time when I did not exist, nor you, nor all these kings; nor in the future shall any of us cease to be.” (BG, Ch 2 text 12, 1983 edition)

Bhagavad Gita As It Is - “As the embodied soul continuously passes, in this body, from boyhood to youth to old age, the soul similarly passes into another body at death. A sober person is not bewildered by such a change." (BG, Ch 2 text 13, 1983 edition)

Bhagavad Gita As It Is - “O son of Kuntī, the nonpermanent appearance of happiness and distress, and their disappearance in due course, are like the appearance and disappearance of winter and summer seasons. They arise from sense perception, O scion of Bharata, and one must learn to tolerate them without being disturbed." (BG, Ch 2 text 14, 1983 edition)

Bhagavad Gita As It Is - “Those who are seers of the truth have concluded that of the nonexistent [the material body] there is no endurance and of the eternal [the soul] there is no change. This they have concluded by studying the nature of both." (BG, Ch 2 text 16, 1983 edition)

Bhagavad Gita As It Is - “That which pervades the entire body you should know to be indestructible. No one is able to destroy that imperishable soul." (BG, Ch 2 text 17, 1983 edition)

Bhagavad Gita As It Is - “Neither he who thinks the living entity the slayer nor he who thinks it slain is in knowledge, for the self slays not nor is slain." (BG, Ch 2 text 19, 1983 edition)

Bhagavad Gita As It Is - "For the soul there is neither birth nor death at any time. He has not come into being, does not come into being, and will not come into being. He is unborn, eternal, ever-existing and primeval. He is not slain when the body is slain." (BG, Ch 2 text 20 “corrected” 1983 edition)

Bhagavad Gita As It Is - "O Pārtha, how can a person who knows that the soul is indestructible, eternal, unborn and immutable kill anyone or cause anyone to kill?" (BG, Ch 2 text 21, 1983 edition)

Bhagavad Gita As It Is - "As a person puts on new garments, giving up old ones, the soul similarly accepts new material bodies, giving up the old and useless ones." (BG, Ch 2 text 22, 1983 edition)

Bhagavad Gita As It Is - "The soul can never be cut to pieces by any weapon, nor burned by fire, nor moistened by water, nor withered by the wind." (BG, Ch 2 text 23, 1983 edition)

Bhagavad Gita As It Is - "This individual soul is unbreakable and insoluble, and can be neither burned nor dried. He is everlasting, present everywhere, unchangeable, immovable and eternally the same." (BG, Ch 2 text 24, 1983 edition)

Bhagavad Gita As It Is - "It is said that the soul is invisible, inconceivable and immutable. Knowing this, you should not grieve for the body." (BG, Ch 2 text 25, 1983 edition)

Bhagavad Gita As It Is - "Some look on the soul as amazing, some describe him as amazing, and some hear of him as amazing, while others, even after hearing about him, cannot understand him at all." (BG, Ch 2 text 29, 1983 edition)

Srila Prabhupada – “There are no new souls, new and old are due to this material body, but the jiva-soul is never born and never dies, so if there is no birth, how can there be new souls?” (Letter to Jagadisa dasa, 7/9/1970)

There is no origin to Krsna's marginal energy (an unlimited number of individual jiva-souls), who have existed for as long as Krsna has existed which is eternity.*.