It is not wrong to feel angry. If someone is continually hurting you and do not want to be fair towards you, it is only natural that you get upset and angry towards that person. The sinful part only occurs when you begin to translate this anger into hate by trying to retaliate, or when you harbour a deep seated bitterness that is not willing to seek forgiveness and reconciliation actively. Note that it did not condemn anger per se. It talks about letting this anger linger on until it turns cancerous and deadly and results in sin - when we take justice into our own hands.
Anger is natural.
Learn to accept the fact that people are not perfect and somethimes we get caught in circumstances that casue us pain, even though we do not deserve it. Surrender this anger over to the Lord in prayer and allow Him to minister to this internal pain so that you may be able to forgive, and in the process of your own healing, learn even to relinquish and love those who have wronged you. In some instances, children may feel responsible for their parents divorce. This could be due to the fights that the parents may have over them. Sometimes, parents openly declare to them that they are splitting up because of irreconcilable differences on parenting.