Families are systems and the members of a family are both individuals and part of a whole; they interact and play off one another. When you think about your family that way, you can see that if one part is skewed a little bit, it will throw the whole system off balance. Since we are all skewed a bit, our family systems can get kind of crazy.
When you think about your family that way, you can also see that its the entire family parenting the children, not just one or two individuals. There are tools you can use to help straighten your family system up a bit.
Roles
Look at the roles people fill in your family. Its ideal to do this before you have kids, because you can readjust roles easier then, but you can still do it even if you have grandkids. Remember, were talking about the entire family parenting the children.
History
What is your familys history, including parents, grandparents, aunts, uncles and cousins? Are there a lot of divorces, affairs, addiction, early deaths? Whats the religious history of your family? How about social or financial status? As you look at your familys history, you may see patterns that alert you to potential problems that could come up in your family.