One of the many downsides I have found after a separation and a family break up is that your child or children end up partly living a separate life from your own. By this, I mean when they are with the other parent and their partner they are, in effect, with another family. This may seem obvious to the outsider but to actually experience it is very painful.
When you have your children you expect, or at least hope, that you can enjoy every aspect of their lives on a daily basis until they leave home. As a family unit you take that for granted. However, when that unit is disbanded that all goes out the window. Your child or children have been robbed of a traditional family and that quite frankly is unfair. They end up spending some time with one parent and sometime with the other and if neither parent can communicate effectively then your child or children will have a partly separate life from you.
To be honest I think it is rare for a family to co-parent effectively when they are not together. If the parent who didn't initiate the separation, they are more than likely to not want to communicate with their ex-partner at all. Basically, pain and emotion felt by the parent dumped upon gets in the way and can cloud the actual job of parenting. It is all about the attitude really and it is very difficult to be co-operative when you have been betrayed.