Legal Question in Family Law in California

No, actually, it is likely to go up. Unlike spousal support in which expenses as well as incomes are taken into account, child support is based on adjusted incomes alone. So the boyfriend's contributions to expenses will not have any impact. What will have an impact, however, is her new child (unless you mean that child was alive and taken into account when your current support was calculated). The child support calculation takes into account how many children you have and comes up with a per-child amount of support you are presumed to owe them on a monthly basis. You are then presumed to be paying that amount for the child when they are with you, and to owe it to the other parent when the child is with them. The per-child amount goes down with the more children you have (since some types of support a child needs, like a home, are shared). So her presumed contribution to the child you have together goes down when she has another child that is not yours. That makes your support go up.