That's a question for God and God alone. Your job is to mind your own damn business. This is not adultery or promiscuity, which damage lives. There is no immorality here. No harm to anyone is caused by a couple remaining faithful and true to one another.
That is where you are so wrong.
Matthew 18:15-18 ESV
“If your brother sins against you, go and tell him his fault, between you and him alone. If he listens to you, you have gained your brother. But if he does not listen, take one or two others along with you, that every charge may be established by the evidence of two or three witnesses. If he refuses to listen to them, tell it to the church. And if he refuses to listen even to the church, let him be to you as a Gentile and a tax collector. Truly, I say to you, whatever you bind on earth shall be bound in heaven, and whatever you loose on earth shall be loosed in heaven.
Ezekiel 33:7-12 ESV
“
So you, son of man, I have made a watchman for the house of Israel. Whenever you hear a word from my mouth, you shall give them warning from me. If I say to the wicked, O wicked one, you shall surely die, and you do not speak to warn the wicked to turn from his way, that wicked person shall die in his iniquity, but his blood I will require at your hand. But if you warn the wicked to turn from his way, and he does not turn from his way, that person shall die in his iniquity, but you will have delivered your soul. “And you, son of man, say to the house of Israel, Thus have you said: ‘Surely our transgressions and our sins are upon us, and we rot away because of them. How then can we live?’ Say to them, As I live, declares the Lord God, I have no pleasure in the death of the wicked, but that the wicked turn from his way and live; turn back, turn back from your evil ways, for why will you die, O house of Israel?
We have an obligation to tell you. My obligation, as have the obligations of so many here who have tried to reprove you, has been met, and yet out of love for another whom we have not even met, we try to steer you from wickedness.