apisvid aste bhagavan sukham vo
yah satvatam kama-dugho ’niruddhah
yam amananti sma hi sabda-yonim
Translation by His Divine Grace A. C. Bhaktivedanta Swami Srila Prabhupada:
May I inquire whether Aniruddha is doing well? He is the fulfiller of all the desires of the pure devotees and has been considered from yore to be the cause of the Rg Veda, the creator of the mind and the fourth plenary expansion of Visnu.
Purport by His Divine Grace A. C. Bhaktivedanta Swami Srila Prabhupada:
Adi-caturbhuja, the original expansions from Baladeva, are Vasudeva, Sankarsana, Pradyumna and Aniruddha. All of Them are visnu-tattvas, or nondifferent Personalities of Godhead. In the incarnation of Sri Rama, all these different expansions appeared for particular pastimes. Lord Rama is the original Vasudeva, and His brothers were Sankarsana, Pradyumna and Aniruddha. Aniruddha is also the cause of Maha-Visnu, from whose breathing the Rg Veda appeared. All this is nicely explained in the Markandeya Purana. In the incarnation of Lord Krsna, Aniruddha appeared as the son of the Lord. Lord Krsna in Dvaraka is the Vasudeva expansion of the original group. The original Lord Krsna never leaves Goloka Vrndavana. All the plenary expansions are one and the same visnu-tattva, and there is no difference in Their potency.