I understand your frustration. The relative obviously knows this will hurt you, but then goes ahead anyway. It further is obvious that there is an intent to hurt, otherwise he or she would not ask you beforehand to forgive. Forgiveness is more difficult when we know that the other intended wrong. Yet, that is why we have this virtue: to offer goodness to others even in the face of injustice. Yours is a case of unambiguous injustice. Forgiveness would be a good idea under this circumstance, knowing it may take longer because of the intent to hurt. At the same time, please consider exercising the virtue of justice by talking with the relative about this pattern of asking for forgiveness before delivering a criticism. If he or she knows it is unjust, then restraining from delivering the criticism is in order.