We turn now to consider the Johannine references, which are five: 1:14, 18, 3:16, 18, and 1 John 4:9. Throughout this section I content that the established meaning of ‘siblingless’ in contexts referring to persons continues to make best sense of these texts, without requiring any particular alteration for this context.
John 1:14, 18
Καὶ ὁ λόγος σὰρξ ἐγένετο καὶ ἐσκήνωσεν ἐν ἡμῖν, καὶ ἐθεασάμεθα τὴν δόξαν αὐτοῦ, δόξαν ὡς μονογενοῦς παρὰ πατρός, πλήρης χάριτος καὶ ἀληθείας
And the Word became flesh, and set up his tent in our midst, and we have seen his glory, the glory of an only-son from a father, full of grace and truth.
I contend that the primary question for us here, given that the immediate context of the word’s usage is παρὰ πατρός, is what reason would there be to not consider the sense of μονογενής to refer to a siblingless son? Every other attestation to this point, when in the context of persons, and familial relations, works with that meaning. If the author of the gospel wanted to indicate, “unique in kind”, or a philosophical “one and only one instance”, they appear to be writing in the wrong key. Similarly, if their intention were to indicate something about the generative process itself, “only begotten”, a more explicitly generative turn of not merely phrase, but context, appears required. Both, or rather either, of those meanings is possible, in a strict sense of possible. However, a reader of the gospel upon encountering μονογενής in close connection to πατρός, is most likely, most naturally, to understand it as a reference to a single and sole son who lacks siblings. The author establishes that this is how to understand the quality or kind of the δόξα that the λόγος possesses and which the author attests to have seen.
This in turn, establishes how to read the second occurrence of μονογενής a few verses later.
θεὸν οὐδεὶς ἑώρακεν πώποτε· μονογενὴς θεὸς ὁ ὢν εἰς τὸν κόλπον τοῦ πατρὸς ἐκεῖνος ἐξηγήσατο.
No-one has ever seen God: God-the-siblingless-son, who is in his father’s bosom, he has made him known.
Two important factors ought to guide our understanding of the term here. First, that the author has just prior used the term in a familial-type context to evoke the way in which an only son bears their father’s glory. Second, that within this same verse it is a familial relationship that is also invoked. This once more suggests that the “unique” reading is lacking in content. Contra Ehrman, there is no need to suppose that the phrase is itself meaningless and therefore must be a later theological correction for μονογενὴς υἱός. Ehrman’s case rests on two bases. The first of these is that external support for μονογενὴς υἱός is strong, beyond the Alexandrian tradition, at least strong enough to argue for its priority. Secondly, that the meaning of μονογενὴς θεός is not understandable within the conceptual world of the Fourth Gospel’s authorship, and only sensible in light of later theological contexts.
I leave aside the textual argument, though the reader should see Kristianto’s paper which walks through the evidence. The theological argument is of more interest here, because Ehrman’s argument is an instance of “lectio difficilior except if it seems too difficult.” Is it not at least likely that a scribe would consider μονογενὴς υἱός a more natural collocation than μονογενὴς θεός and correct it in that direction? Similarly, while we do not need to import 4th century, or even 3rd or 2nd century, christologies into John, nor should we assume that the gospel’s author is incapable of using the term μονογενής to expresses the idea that God (the siblingless son) makes God (the father) known.
John 3:16, 18
The second pair of instances in John occur in swift succession, again in connection to each other.
16 Οὕτως γὰρ ἠγάπησεν ὁ θεὸς τὸν κόσμον, ὥστε τὸν υἱὸν τὸν μονογενῆ ἔδωκεν, ἵνα πᾶς ὁ πιστεύων εἰς αὐτὸν μὴ ἀπόληται ἀλλʼ ἔχῃ ζωὴν αἰώνιον. 17 οὐ γὰρ ἀπέστειλεν ὁ θεὸς τὸν υἱὸν εἰς τὸν κόσμον ἵνα κρίνῃ τὸν κόσμον, ἀλλʼ ἵνα σωθῇ ὁ κόσμος διʼ αὐτοῦ. 18 ὁ πιστεύων εἰς αὐτὸν οὐ κρίνεται· ὁ δὲ μὴ πιστεύων ἤδη κέκριται, ὅτι μὴ πεπίστευκεν εἰς τὸ ὄνομα τοῦ μονογενοῦς υἱοῦ τοῦ θεοῦ.
For God loved the world so, that he gave his only son, that everyone believing in him should not perish but have eternal life. For God did not send his son into the world to condemn the world, but that the world be saved through him. The one that believes in him is not condemned; condemned already, however, is the unbelieving person, because they have not believed in the name of God’s siblingless son.
Given the prior usage in John 1, the lack of any significant shift to a philosophical register here, and that both uses here modify υἱός, what reason is there to overturn the significant weight of common usage, and instead find a peculiarly Johannine theological meaning of “uniquely begotten”, except on the supposed basis of John 1? Which basis we have already addressed.
1 John 4:9
ἐν τούτῳ ἐφανερώθη ἡ ἀγάπη τοῦ θεοῦ ἐν ἡμῖν,
ὅτι τὸν υἱὸν αὐτοῦ τὸν μονογενῆ ἀπέσταλκεν ὁ θεὸς
εἰς τὸν κόσμον ἵνα ζήσωμεν διʼ αὐτοῦ. 
By this the love of God is made manifest in us,
that God has sent his only son,
into the world, so that we may live through him.
The author of 1 John uses μονογενής in a very Johannine manner, echoing the language of John 3 above. Insofar as there is no significant alteration from the usage in the gospel, neither is there a change in signification here. For this author, Jesus is the μονογενὴς υἱός because there are no other υἱοί of the same kind. For this same reason they reserve the term υἱός for Jesus, employing τέκνα instead to refer to believers.
 To take pains to make this obvious, when the word is taken to indicate “one of a kind” or “unique”, there must be some sense in which the referent is one of a kind. That sense is, for μονογενής, the lack of siblings. Which gives the word more content than the simple “unique” does.
 Ehrman, Bart D. The Orthodox Corruption of Scripture: The Effect of Early Christological Controversies on the Text of the New Testament, (New York: Oxford Univ. Press, 1993), 78-82.
 Kristianto, S. ‘E valuating Bart Ehrman’s Textual Reconstruction: A Test Case on John 1:18’ Asia Journal of Theology, (31)1, (2017): 23-35.
 Without necessarily resolving or pre-empting how the author understands those relations to work.