It is interesting to note that the angels were not born in the flesh as humans, and they are not "born again" like us human believers are.  Jesus Christ was pre-existent with God, the Father, and the only "begotten Son of God who later was born as a human when the Holy Spirit overshadowed Mary (Luke 1:31-35) while we believers were born as humans and reborn by the power of the Holy Spirit.  No angel can make the claim that they were later born as humans nor can they be born again in the spirit by the power of the Holy Spirit (John 3:3-8).  No angel can call himself "the only begotten Son" of God, the Father who was born as a human although the angels are called the sons of God in Genesis 6, and can never be the begotten Son of God, or a begotten son of God like us believers.

JESUS CHRIST, THE BEGOTTEN SON OF GOD

Hebrews 1:5, "For unto which of the angels said he at any time, Thou art my Son, this day have I begotten thee? And again, I will be to him a Father, and he shall be to me a Son?" In this verse, "begotten" is Greek gematria G1080 

https://www.biblewheel.com/GR/GR_Database.php?bnum=58&cnum=1&vnum=5 and "The Holy Spirit" is G1080

according to https://biblewheel.com/GR/GR_1080.php

In the 2 following Bible verses, the word "begotten" is G1080 which is the same as "The Holy Spirit" G1080.

Hebrews 5:5, "So also Christ glorified not himself to be made an high priest; but he that said unto him, Thou art my Son, today have I begotten thee." 

https://www.biblewheel.com/GR/GR_Database.php?bnum=58&cnum=5&vnum=5

Act 13:33 God hath fulfilled the same unto us their children, in that he hath raised up Jesus again; as it is also written in the second psalm, Thou art my Son, this day have I begotten thee. https://www.biblewheel.com/GR/GR_Database.php?bnum=44&cnum=13&vnum=33

THOSE BORN AGAIN BY THE HOLY SPIRIT THAT ARE BEGOTTEN OF HIM:

 

In the following verses, the word "begotten" is G1080 which is the same as "The Holy Spirit" G1080:

1Co 4:15 For though ye have ten thousand instructors in Christ, yet have ye not many fathers: for in Christ Jesus I have begotten you through the gospel." https://www.biblewheel.com/GR/GR_Database.php?bnum=46&cnum=4&vnum=15

1 John 5:1 "Whosoever believeth that Jesus is the Christ is born of God: and every one that loveth him that begat loveth him also that is begotten of him." In this verse, "That is begotten" is "gennao" in Greek, and has a Greek gematria of G1080 according to  https://www.biblewheel.com/GR/GR_Database.php?bnum=62&cnum=5&vnum=1 and 

"The Holy Spirit" is also G1080  The Number 1080 - The Holy Spirit

1 John 5:8, "We know that whosoever is born of God sinneth not; but he that is begotten of God keepeth himself, and that wicked one toucheth him not."  "He that is begotten" in this verse is "gennao" in Greek, and has a Greek gematria of G1080 according to https://www.biblewheel.com/GR/GR_Database.php?bnum=62&cnum=5&vnum=18 and "The Holy Spirit" is also G1080  The Number 1080 - The Holy Spirit

The angels are the sons of God in Genesis 6:2 & 6:4, but are not begotten sons of God like us believers, and not the begotten Son of God, Jesus Christ.  

"The sons of God" in Genesis 6:4 who went into the daughters of men, and procreated the giants are called "Ben Elohim" according to Full Text Hebrew/Greek Bible Gematria Database  The phrase "That the sons" is H1121 in Strong's concordance which is "Ben," and "of God" is H0430 which is "Elohim" meaning "God."  "The sons of God" in John 1:12 and in other New Testament verses in Greek are called "Teknon Theos" according to Full Text Hebrew/Greek Bible Gematria Database "Teknon" is G5043 in Strongs concordance which can mean "offspring, son, daughter." "Theos" is G2316 meaning "of God." We believers are the sons of God in the New Testament verses.

Hebrews 1:5 says, "For unto which of the angels said he at any time, Thou art my Son, this day have I begotten thee? And again, I will be to him a Father, and he shall be to me a Son?"  "Son" in this verse is a different word in Greek

than "Teknon" according to Full Text Hebrew/Greek Bible Gematria Database  "Huios" is the Greek G5207 word for "Son" in this verse. It refers to the Son of Man or the Son of God.  So Hebrews 1:5 would be better explained as "For unto which of the angels said he at any time, Thou art my Son, (meaning the Son of God), this day have I begotten thee: And again, I will be to him a Father, and he shall be to me a Son?" (meaning the Son of man or the Son of God.)  Jesus is the only begotten Son of God born of the virgin Mary, and no angel can ever the "the only begotten Son of God."