What is the punishment for revealing secrets and disclosing common matters that occur between siblings with the intention of causing discord and separation, even if the disclosure is a lie?

Divulging a secret is a betrayal of trust (amanah), and it is forbidden (haram) if it results in harm. It is considered baseness if it does not result in harm.

The Prophet, peace and blessings be upon him, mentioned the consequences of tale-bearing (namimah), among which are: torment in the grave, that the tale-bearer is among the worst of God's servants, and that he will not enter Paradise.

Tale-bearing is revealing what one dislikes to be revealed, whether it be a statement or an action, and whether it be a defect or not. There is no specific prescribed punishment for tale-bearing in this world, but those in authority (wulat al-umur) have the right to discipline those who commit sins.