This was a manifestation of Jesus in the OT. Though Jews would reject that, what we can agree on is that it is not in reference to Ezra. Furthermore sons of God is used to describe many in the Bible.
While the Jews were looking for a promised son, the subject you mention here could be the reference the Quran makes:
Surah 9.30 The Jews call 'Uzair a son of Allah...
Which I always took to mean that Muslims are prohibited from even recognizing "sons of God" like you and I.
As in this reference:
John 1:11 He came unto his own, and his own received him not. 12 But as many as received him, to them gave he power to become the sons of God, [even] to them that believe on his name:
http://www.islamandthetruth.com/gospel_of_john.htm
Though I have to correct myself and take that back, since I just checked other translations and the article "the" is used:
9.030
YUSUFALI: The Jews call 'Uzair
a son of Allah, and the Christians call Christ the son of Allah. That is a saying from their mouth; (in this) they but imitate what the unbelievers of old used to say. Allah's curse be on them: how they are deluded away from the Truth!
All the rest are more clear regarding the singular entity:
PICKTHAL: And the Jews say: Ezra is
the son of Allah, and the Christians say: The Messiah is the son of Allah. That is their saying with their mouths. They imitate the saying of those who disbelieved of old. Allah (Himself) fighteth against them. How perverse are they!
SHAKIR: And the Jews say: Uzair is
the son of Allah; and the Christians say: The Messiah is the son of Allah; these are the words of their mouths; they imitate the saying of those who disbelieved before; may Allah destroy them; how they are turned away!
ASAD 9:30 AND THE JEWS say, "Ezra is
God's son," while the Christians say, "The Christ is God's son." Such are the sayings which they utter with their mouths, following in spirit assertions made in earlier times by people who denied the truth! [44] [They deserve the imprecation:] "May God destroy them!" [45] How perverted are their minds! [46]