Srimad-Bhagavatam: Canto 3 - Chapter 1 - Verse 52


एवं युक्तकृतस्तस्य दैवञ्चावेक्षतस्तदा ।कस्य रूपमभूद् द्वेधा यत्कायमभिचक्षते ॥ ५२ ॥


evaṁ yukta-kṛtas tasyadaivaṁ cāvekṣatas tadākasya rūpam abhūd dvedhāyat kāyam abhicakṣate


While he was thus absorbed in contemplation and was observing the supernatural power, two other forms were generated from his body. They are still celebrated as the body of Brahmā.


Two bodies came out from the body of Brahmā. One had a mustache, and the other had swollen breasts. No one can explain the source of their manifestation, and therefore until today they are known as the kāyam, or the body of Brahmā, with no indication of their relationship as his son or daughter.