SB 10.34.4

ūṣuḥ sarasvatī-tīre
 jalaṁ prāśya yata-vratāḥ
rajanīṁ tāṁ mahā-bhāgā
 nanda-sunandakādayaḥ
Word for word: 
ūṣuḥ — they stayed; sarasvatī-tīre — on the bank of the Sarasvatī; jalam — water; prāśya — subsisting on; yata-vratāḥ — taking strict vows; rajanīm — the night; tām — that; mahā-bhāgāḥ — the greatly fortunate ones; nanda-sunandaka-ādayaḥ — Nanda, Sunanda and the others.
Translation: 
Nanda, Sunanda and the other greatly fortunate cowherds spent that night on the bank of the Sarasvatī, strictly observing their vows. They fasted, taking only water.
Purport: 

Śrīla Viśvanātha Cakravartī explains that Sunanda is the younger brother of Nanda Mahārāja.