CC Ādi 9.21

vṛkṣera upare śākhā haila dui skandha
eka ‘advaita’ nāma, āra ‘nityānanda’
Synonyms: 
vṛkṣera — of the tree; upare — on the top; śākhā — branch; haila — became; dui — two; skandha — trunks; eka — one; advaita — Śrī Advaita Prabhu; nāma — of the name; āra — and; nityānanda — Nityānanda Prabhu.
Translation: 
At the top of the tree the trunk branched into two. One trunk was named Śrī Advaita Prabhu and the other Śrī Nityānanda Prabhu.