Always Being Together, and Always Working Together

Quoting from Delighting in the Trinity: An Introduction to the Christian Faith by Michael Reeves:
Before creation, before all things, … the Father was loving and begetting his Son. For eternity, that was what the Father was doing. He did not become Father at some point; rather, his very identity is to be the one who begets the Son. That is who he is. Thus it is not as if the Father and the Son bumped into each other at some point and found to their surprise how remarkably well they got on. The Father is who he is by virtue of his relationship with the Son. Think again of the image of the fountain: a fountain is not a fountain if it does not pour forth water. Just so, the Father would not be the Father without his Son (whom he loves through the Spirit). And the Son would not be the Son without his Father. He has his very being from the Father. And so we see that the Father, Son, and Spirit, while distinct persons, are absolutely inseparable from each other. Not confused, but undividable. They are who they are together. They always are together, and thus they always work together.
So the Father could not exist without the Son or the Spirit. His very identity comes from his relationship with them. Same thing for the Son and the Spirit. The are who they are because they are eternally in relationship with the other members of the Trinity.