मम योनिर्महद्ब्रह्म तस्मिन् गर्भं दधाम्यहम्।संभवः सर्वभूतानां ततो भवति भारत॥
mama yonir mahad brahma tasmin garbhaṃ dadhāmy ahamsambhavaḥ sarva-bhūtānāṃ tato bhavati bhārata
Word by word
The verse says
My womb is the great nature. In it I place the seed, and from that the birth of all beings follows, Arjuna.
In plain words
Two parents, in one line, and both are him.
Mama yonir mahad brahma — the great nature is my womb. And then: I place the seed.
The image is deliberately biological, and it is being used for the origin of everything.
Where you've felt this · in family life
Nobody in your family can say which side your temper comes from, because both sides had it. The question of who you got it from has no answer. It was in the material on both sides of the arrangement before you were anywhere.
Going deeper
Occupying both halves of a reproductive image at once is a strange thing to write, and Chapter 9 did it too.
There, the line was: I am the father of this world, and the mother. Here the structure is the same but more technical — nature is the womb, he places the seed. The point of taking both positions is to rule out a picture in which spirit acts on matter from outside, as a maker on material.
Chapter 13 had already said both are without beginning, which makes any story of one producing the other difficult.
What this gives a reader is a way of thinking about their own existence that is neither accident nor manufacture. On this account you are not something made by somebody, and you are not something that happened. You are the outcome of a meeting that has been going on for as long as there has been anything.