In the Holy Shri Shiv Puran, as published by Gita Press Gorakhpur and translated by Shri Hanuman Prasad Poddar, the following is described:
In Chapter 6, Rudra Sanhita, page 100, it is mentioned that ParBrahm, who is formless, manifests as God SadaShiv, his bodily form. From SadaShiv, a Shakti emerged, known as Ambika or Prakriti (Durga), the mother of the three gods—Shri Brahma, Shri Vishnu, and Shri Shiv—also called Tridev Janni. She has eight arms. SadaShiv, also referred to as Shiv, Shambhu, and Maheshwar, covers himself in ash. This Kaal-form Brahm created an area called Shivlok, where he and Durga, acting as husband and wife, gave birth to a son named Vishnu (page 102).
In Chapter 7, page 103, Brahma states that he, too, was born from the union of God SadaShiv (Kaal-Brahm) and Prakriti (Durga). He was rendered unconscious afterward.
In Chapter 9, page 110, it is further explained that Brahma, Vishnu, and Rudra (Shiv) possess the three gunas (qualities), while Shiv (Kaal-Brahm) is beyond these qualities.
Thus, it is established that Brahma, Vishnu, and Shiv originated from SadaShiv (Kaal-Brahm) and Prakriti (Durga). Durga is their mother, and Brahm (Jyoti Niranjan) is their father. These three gods represent the qualities of Rajgun (Brahma), Satgun (Vishnu), and Tamgun (Shiv).