In my experience, no family is perfect, and I suspect most families have at least some conflict and tension from time to time. After Adam and Eve sinned in the Garden of Eden, the first problem they faced was conflict in their family first between themselves, and then between their two sons (see Genesis 3:12; 4:8).
What is the problem? Many answers have been given: rivalry between children as they are growing up; jealousy; anger; insensitivity; unfair or harsh treatment the list is almost endless. And each of them may contain an element of truth, depending on the situation.
But if you are a Christian you know there's a deeper problem the problem of the human heart. Down inside, we each want our own way, and when someone blocks us we get upset and want to strike back. The Bible says, "What causes fights and quarrels among you? Don't they come from your desires that battle within you?" (James 4:1).
Pray for your family, and ask God to help you be a peacemaker by pointing them to Christ. Go out of your way to show kindness to them the kindness of Christ. Even if you don't seem to make progress at first, God will honor you for making the effort.