If we do not forgive/loose the sins committed against us by a brother on earth when they ask, that sin is bound on earth as well as in heaven and God cannot forgive/loose our sins against Him.
Jesus explains this in Mathew 18 15-35. The first example involves one brother asking another brother to forgive him and how to handle it if that brother refuses. The only role the local church has in this is as a referee. They are not required to forgive anyone because they were not the one sinned against.
They second example is when Peter asks Jesus how many times he/Peter has to forgive a brother who sins against him/Peter. Jesus tells Peter seven times seventy and goes on to explain the concept of binding and loosing. You and I have to forgive our earthly brothers before we can be forgiven by our heavenly Father.
What you won't find here or anywhere else is where Jesus tells Peter or any other man he can forgive sins committed against God for God as the Catholic Church practices.
Only you and I can, and must, forgive sins committed against us by a brother. Only God can forgive our sins committed against Him. BVB
Matthew 18:15-34 (New King James Version)
Dealing with a Sinning Brother
15 “Moreover if your brother sins against you, go and tell him his fault between you and him alone. If he hears you, you have gained your brother. 16 But if he will not hear, take with you one or two more, that ‘by the mouth of two or three witnesses every word may be established.’[a] 17 And if he refuses to hear them, tell it to the church. But if he refuses even to hear the church, let him be to you like a heathen and a tax collector.
18 “Assuredly, I say to you, whatever you bind on earth will be bound in heaven, and whatever you loose on earth will be loosed in heaven.
19 “Again I say[b] to you that if two of you agree on earth concerning anything that they ask, it will be done for them by My Father in heaven. 20 For where two or three are gathered together in My name, I am there in the midst of them.”
The Parable of the Unforgiving Servant
21 Then Peter came to Him and said, “Lord, how often shall my brother sin against me, and I forgive him? Up to seven times?”
22 Jesus said to him, “I do not say to you, up to seven times, but up to seventy times seven. 23 Therefore the kingdom of heaven is like a certain king who wanted to settle accounts with his servants. 24 And when he had begun to settle accounts, one was brought to him who owed him ten thousand talents. 25 But as he was not able to pay, his master commanded that he be sold, with his wife and children and all that he had, and that payment be made. 26 The servant therefore fell down before him, saying, ‘Master, have patience with me, and I will pay you all.’ 27 Then the master of that servant was moved with compassion, released him, and forgave him the debt.
28 “But that servant went out and found one of his fellow servants who owed him a hundred denarii; and he laid hands on him and took him by the throat, saying, ‘Pay me what you owe!’ 29 So his fellow servant fell down at his feet[c] and begged him, saying, ‘Have patience with me, and I will pay you all.’[d] 30 And he would not, but went and threw him into prison till he should pay the debt. 31 So when his fellow servants saw what had been done, they were very grieved, and came and told their master all that had been done. 32 Then his master, after he had called him, said to him, ‘You wicked servant! I forgave you all that debt because you begged me. 33 Should you not also have had compassion on your fellow servant, just as I had pity on you?’ 34 And his master was angry, and delivered him to the torturers until he should pay all that was due to him.