In the OT, the Jewish God YHWH, says "you are my firstborn. Today I have begotten you."
Since religious texts are full of metaphor, you can easily reconcile these two passages -- YHWH/Allah is childless is some sense, but has children in another.
You can spin differences between all three religions, and within their various sects, or you can spin common ground. It all depends on how you wish to spin it, for whatever political purpose.
1 John 2:22 Who is a liar but he that denieth that Jesus is the Christ? He is antichrist, that denieth the Father and the Son.
1 John 4:3 And every spirit that confesseth not that Jesus Christ is come in the flesh is not of God: and this is that spirit of antichrist, whereof ye have heard that it should come; and even now already is it in the world.
2 John 1:7 ¶For many deceivers are entered into the world, who confess not that Jesus Christ is come in the flesh. This is a deceiver and an antichrist.
Translations of Qur'anic Verses by Abdullah Yusuf Ali:
Say: "Praise be to Allah Who begets no son and has no partner in (His) dominion: nor (needs) He any to protect Him from humiliation: Yea magnify Him for His greatness and glory!" 17: 111
Further that He may warn those (also) who say "Allah hath begotten a son": 18: 4
It is not befitting to (the majesty of) Allah that He should beget a son. Glory be to Him! When He determines a matter He only says to it "Be" and it is. 19: 35
They say: "(Allah) Most Gracious has begotten a son!" Indeed ye have put forth a thing most monstrous! 19: 88/89
For it is not consonant with the majesty of (Allah) Most Gracious that He should beget a son. 19: 92
No son did Allah beget nor is there any god along with Him: (if there were many gods) behold each god would have taken away what he had created and some would have lorded it over others! Glory to Allah (He is free) from the (sort of) things they attribute to Him! 23: 91
He begetteth not nor is He begotten; 112: 3