The protection of a Muslim's blood and the killing of a child by his relatives or parents

Question:
And I said: Shaykh, may Allah reward you. Sometimes a child may harm others and they are grateful to him, whether he is a daughter or a son. Then his relatives agree to kill him, or one of the parents kills him, or the parents kill him. So, is retaliation required of the relatives for killing him, or of the parents?

Answer:
If he is a Muslim, a Muslim must not be killed. Whoever intentionally kills him, retaliation is obligatory against him. As for if his father kills him, you have heard that there is no retaliation for a father who kills his child. As for whoever kills him other than the father, and he is a Muslim, a Muslim's blood is protected; it is not permissible [to kill him], even if he is an open sinner, even if he is an open sinner, even if he has foul language and bad behavior, as long as he is a Muslim and has not left the religion of Islam, his blood is protected. Yes. It may be that this constitutes a breach of security, yes.