bhrataram nandam agatam
jnatva datta-karam rajne
vasudevah—Vasudeva; upasrutya—when he heard; bhrataram—that his dear friend and brother; nandam—Nanda Maharaja; agatam—had come to Mathura; jnatva—when he learned; datta-karam—and had already paid the taxes; rajne—unto the King; yayau—he went; tat-avamocanam—to the residential quarters of Nanda Maharaja.
When Vasudeva heard that Nanda Maharaja, his very dear friend and brother, had come to Mathura and already paid the taxes to Kamsa, he went to Nanda Maharaja’s residence.
Vasudeva and Nanda Maharaja were so intimately connected that they lived like brothers. Furthermore, it is learned from the notes of Sripada Madhvacarya that Vasudeva and Nanda Maharaja were stepbrothers. Vasudeva’s father, Surasena, married a vaisya girl, and from her Nanda Maharaja was born. Later, Nanda Maharaja himself married a vaisya girl, Yasoda. Therefore his family is celebrated as a vaisya family, and Krsna, identifying Himself as their son, took charge of vaisya activities (krsi-go-raksya-vanijyam [Bg. 18.44]). Balarama represents plowing the land for agriculture and therefore always carries in His hand a plow, whereas Krsna tends cows and therefore carries a flute in His hand. Thus the two brothers represent krsi-raksya and go-raksya.
Link to this page: https://prabhupadabooks.com/sb/10/5/20