Regarding Krishna's "Sun God" status:

As Srivastava points out regarding sun-worship overall in Indian religious tradition:

" ...the Sun as an object of worship attracted the attention of mankind in the Neolithic period in India, as is the case with Europe also...

[ Srivastava, V.C., Sun Worship in Ancient India, 1972, p341 ]

In the 'Gayatri', a holy Vedas text, it reveals the sun as the Supreme Godhead:

"Let us adore the supremacy of that divine Sun, the Godhead who illuminates all, who recreates all, from whom all proceed, to whom all must return; whom we invoke to direct our understanding aright in our progress toward his holy seat"

[ Moor, Edward: The Hindu Pantheon, W.O. Simpson p377 ]

In the Bhagavad-Gita, verse 10.21, Krishna states:

"I am Vishnu, striding among sun gods, the radiant sun among lights..."

And at 15.12. Krishna Says:

"Know that my brilliance, flaming in the sun, in the moon, and in fire, illuminates this whole universe"
[ Acharya S. Suns of God, p186 ]

*****

Regarding Krishna's "Virgin Birth" status:

Even though it is obvious that Krishna was another form of Vishnu ( see quote below ), it is still argued that because Devaki had other children prior to the birth of Krishna, she was not a virgin.

"Eulogized by the Gods, Devaki bore in her womb the lotus-eyed deity, the protector of the world...No person could bear to gaze upon Devaki, from the light that invested her, and those who contemplated her radiance felt their minds disturbed. The gods invisible to mortals, celebrated her praises continually from the time that Vishnu was contained in her person"

[ Vishnu Parana, translated by H. Wilson, london 1840, p 502 ]

What first needs to be understood is that the "Virgin Purity" of the "mortal mother of god" in the Pagan world was the traditional norm.

As Carpenter points out:
"There is hardly a god whose worship as a benefactor of mankind attained popularity in any of the four continents... who was not reported to have been born from a virgin, or at least from a mother who owned the child not to any earthly father."

[ Carpenter, Edward: Pagan and Christian Creeds, Chapter 10, page 115 ]

Now- understanding that virgin/miracle conception can be found throughout religious history as a staple of the birth of the God-man, the idea that Devaki is not a virgin based on the fact she had other children does not alter this notion because, in fact, Jesus's mother, the "virgin" Mary, also is denoted as having prior children. Though this understanding is out of the mainstream for most Christians, a literalist view of the Bible dictates that Jesus had brothers. For example, Matthew 12:46 refers to Jesus's "brothers":

"While he ( Jesus ) was still speaking to the people, behold his mother and his brothers stood outside, asking to speak with him" -Matt 12:46

While at Matt 13:55-56:
"Is not this the carpenter's son? Is not his mother called Mary? And are not his brothers James and Joseph and Simon and Judas? And are not all his sisters with us?"

The bottom line is the age old motif expressed regarding the Son of God, born of a mortal woman and fathered by God himself, carries with it the Perpetual Virgin status, which has been recognized for many centuries. The Virgin Mary is a perpetual virgin and so is Devaki.

And as Jones points out:

...as Crishna revealed himself to Arjun, or in a human form, which Crishna usually bore; and in that mode of appearing, the deities are generally supposed to be born of a woman, but without carnal intercourse."

[ Jones, Sir William, Asiatic Researches, Cosmo Pub[1788-1839] p.373 ]

"Crishna was born of a Chaste virgin, called Devaki, who, on account of her purity was selected to become the" mother of God"

[ Doane, Thomas: Bible Myths and Their Parallels in Other Religions, p. 113 ]

However, all assumptions aside, the most revealing aspect is just as Jesus's coming was said to have been prophesied as the coming 'Messiah to be born of a virgin, so was Krishna's; this prophesy said the "soul of the universe"was to be born of a Virgin" As Acharys S describes:

' The Pourourava speaks of the "divine Paramatma ( soul of the universe) being " born of a virgin who shall be fecundated by the thought of Vishchnou". Moreover, the Vedanta relates that during the "early part" of the Kali-Yuga, which began 5000 yrs ago, "shall be born the son of the virgin", i.e. Krishna.
...these scriptures have been purported to be "prophecies"; in reality, they lay down a blueprint for a myth about a savior who is to be born of a virgin. '

[ Acharya S.: Suns of God , Adventures Unlimited Press, 2004. p218 ]

For much more on these points, see Acharya S, Suns of God Chapters 6-9