Kṛṣṇa told Yogamāyā that He would appear from the womb of Devakī (aṁśa-bhāgena devakyāḥ) and she (Yogamāyā) would appear from the womb of Yaśodā. Brahmā played a part in Kṛṣṇa’s appearance by praying at the milk ocean. Baladeva played a part by first making arrangements for Kṛṣṇa to appear within the womb of Devakī. Yogamāyā played a part by transferring the pregnancy of Baladeva from Devakī’s womb to Rohiṇī’s womb. Thus jīva-tattva, viṣṇu-tattva and śakti-tattva are all integrated with Kṛṣṇa and when He appears, He appears with all His integrated parts. Thus the word aṁśa-bhāgena is used in this verse. The word also means that knowledge, strength and other qualities (aṁśa) accompany (bhaga means bhajana) the Lord so that He manifests completely. He is perfect in whom all parts (aṁśa) enter (bhajana:praveśa). Another meaning is that aṁśa refers to Brahmā and all other servants and bhāga refers to auspiciousness. The Lord appears for the auspiciousness of Brahmā and others. Another meaning is that Kṛṣṇa would appear as the son of Devakī partially (aṁśa) manifesting Himself but not completely since Devakī would love Him with aiśvarya bhāva. Yaśodā, however, would manifest pure parental love.
Kṛṣṇa appeared simultaneously as the son of Devakī and as the son of Yaśodā, and Yogamāyā appeared as the daughter of Yaśodā, when Vasudeva was about to carry Kṛṣṇa to the home of Nanda. Two children appeared from Yaśodā at different times. This is confirmed in SB 10.4.9 which describes Yogamāyā as ānujā, the younger sister of Kṛṣṇa. Kṛṣṇa appeared before Yaśodā with two hands. Vasudeva was not in the position of pure affection for Kṛṣṇa and thus Kṛṣṇa first appeared as Viṣṇu before Vasudeva. Yaśodā pleased her son Kṛṣṇa without understanding His Godhood and thus she was elevated. When Kṛṣṇa was born of Yaśodā everyone was asleep by the influence of Yogamāyā. Even Yaśodā was asleep. Without any pain she gave birth to Kṛṣṇa. At the same time, Devakī gave birth to four handed Viṣṇu. Yogamāyā kept Kṛṣṇa hidden, and Vasudeva did not see Yaśodā’s son but saw only the daughter. When Vasudeva put his son on the lap of Yaśodā, that son entered into Yaśodā’s son, who was already there. All plenary portions and portions of plenary portions enter into the original Lord.
Yogamāyā is the Lord’s svarūpa-śakti, having the ability to do the impossible. Though she does not pay attention when Kṛṣṇa in Vraja is agitated by His devotees’ affection, Kṛṣṇa has her invisibly assist in the pastimes at all times, acting favorably to Him. This implies that Kṛṣṇa’s show of emotions to His devotees is real, not orchestrated by Yogamāyā. Kṛṣṇa appeared with four hands from Devakī and with two hands from Yaśodā. When Devakī asked Kṛṣṇa to cover His four-armed form, Yogamāyā who remained in Yaśodā’s womb, assumed a formless feature and took Yaśodā’s son to Mathurā, and this two-armed Kṛṣṇa came to Devakī and merged the four-armed form into Himself. The four-armed form is considered Viṣṇu by some, but Rūpa Gosvāmī in Laghu Bhāgavatāmṛta says it is Kṛṣṇa with four hands.
Although all forms of God are one, due to varieties of rasa there are still different appearances of God. There are seven types of sweetness pertaining to the transcendental form of the Lord: sweetness of form, touch, smell, sound and taste, the sweetness of the Lord’s affection for the devotee (bhakta-vatsalya) and the sweetness of His pastimes (līla-mādhuri). The sweetness of Vraja as two additional types: Kṛṣṇa’s flute (veṇu-mādhuri) and His loving exchanges with His associates (prema-mādhuri). In Vraja Kṛṣṇa displays rūpa-mādhurya, līlā-mādhurya, prema-mādhurya and veṇu-mādhurya.
There are 4 types of prema: dāsya, sakhya, vātsalya and mādhurya. The glory of vātsalya-prema is that it makes Kṛṣṇa the object of pity and extreme attachment. Although Kṛṣṇa’s majesty is present, the mood of vātsalya covers it in such a way that Kṛṣṇa becomes subservient and bound by the ropes of attachment. In return Kṛṣṇa gives those devotees a taste of sweetness unavailable to others. The taste arising from such intense attachment is millions of times more than that experienced thru jñāna or jñānamayī-rati. Because of great attachment a mother derives more pleasure from her son though he is full of faults, than from seeing the full moon which extinguishes all suffering and bestows all bliss. If that is so, just imagine the bliss of having the Supreme Lord as a son. This is the difference between jñāna and prema