Sibling rivalry is a completely normal occurrence. All siblings go through it to some extent or another. There is jealousy and competition that is felt and that can lead to bickering and fighting. It can also depend on individual personalities of your children. Some children are more laid back and others are easily flustered. All of these things can lead to inevitable quarreling among siblings.
Try To Stay Out of It
When a fight between siblings unfolds, whenever possible, don’t get involved. Unless there are issues of safety then try not to be a part of their disagreement. If you are always stepping in to stop fights then they will not be able to learn to work out their own problems. They need to learn to work things out themselves and resolve conflicts.
Make sure to give each child individual time and praise. Let them know privately each of their own individual strengths and give encouragement. Every child is different and has their own characteristics so each one needs a different approach. But doing this will let them know you value their uniqueness and they will be less likely to feel shortchanged compared to another sibling.
Get Them Involved
If it’s a matter of an older sibling feeling jealous of a newer sibling then give them tasks to do that they can help you with, such as, feeding the baby, bringing diapers, holding and cuddling the baby, etc. Or plan family activities that will get the younger child and older child working together and learning to share. As you do these things they will feel valued and learn to care more about their sibling and want to help each other.
Be a Role Model
The way that parents resolve problems and disagreements sets a strong example for kids. If you as a couple are yelling, slamming doors, or calling each other names then that is the way your children will think is appropriate to resolve their own conflicts. But if you resolve problems respectfully, productively, and non-aggressively then your children will learn to do those things themselves when they run into problems.
Brazelton, T. Berry. (2006). Touchpoints. Cambridge, Massachusetts: Da Capo Press.