Siblings bicker a lot. As much as it drives parents crazy, it is a part of natural life. This often gets even more intense when they are going through their parent's divorce. At this point, you need to think about ways that you can minimize the effects of the sibling rivalry. Not only can this help to keep the peace, but it can also help your children to learn to thrive in all situations.
One of the primary things that will cause the children to battle each other is attention. They will all want to fight over the attention that their parents give. As a parent, you might want to divide your attention between them evenly. This isn't always the case. Each of them will have different needs during the divorce, so you have to take that into consideration when you are determining how to divide your attention.
Another issue that comes up a lot in these cases is that the children will want to blame the adults, each other and themselves for the issues that caused the divorce. You have to find ways to reassure them that it was situations and not people that ultimately led to the end of the marriage. You don't have to give them all the details of the issue, but you can provide them with age-appropriate information that can help to put these concerns to rest.
You and your ex might need to work as a parenting team to address these problems with the siblings who can't seem to get along. Trying to forge those meaningful relationships between the kids now can boost them as they get older.