'Him I sang praises to, therefore art thou my only son,' thus said Kaushîtaki to his son. 'Do thou therefore sing praises to the breath as manifold, if thou wishest to have many sons.'

In plain words: Kaushitaki told his son that he had worshipped breath as only one thing, and so he had only one son. He told his son to honor breath in its many forms if he wanted many sons.