Saṁjñā, the wife of Vivasvān, the sun-god, gave birth to the Manu named Śrāddhadeva, and the same fortunate wife also gave birth to the twins Yamarāja and the river Yamunā. Then Yamī, while wandering on the earth in the form of a mare, gave birth to the Aśvinī-kumāras.
Srimad Bhagavata Purana
श्रीमद्भागवतमहापुराणम्
मूल श्लोकः
विवस्वतः श्राद्धदेवं संज्ञासूयत वै मनुम् । मिथुनं च महाभागा यमं देवं यमीं तथा । सैव भूत्वाथ बडवा नासत्यौ सुषुवे भुवि
vivasvataḥ śrāddhadevaṃ saṃjñāsūyata vai manum | mithunaṃ ca mahābhāgā yamaṃ devaṃ yamīṃ tathā | saiva bhūtvātha baḍavā nāsatyau suṣuve bhuvi
SB 6.6.40