In California, if one parent has another child from a different relationship, this can lead to a modification of the child support agreement. The new child may result in a change in the parent's financial situation. If this change is significant, the court may modify the child support agreement to reflect the new financial situation due to changes in income, expenses, and the amount of time the parent can spend with the child.
However, it is crucial to remember that the court will only modify a child support agreement if circumstances have changed considerably. A modification will not be granted simply because a parent has a new child but because the new child has significantly changed the parent's financial situation.