Legal Question in Family Law in California

If you and your girlfriend are living together with the children, she generally will not be able to get child support any more than a new wife could. You yourself are entitled to a hardship deduction, however, for children of a new relationship that you live with and support. So you should file for a modification of support on that basis. If you are not living together, yes, it is legal for her to file for support and you would probably be much better off to get an order to pay her support instead of just supporting her children off the record.

An order to pay support to your new girlfriend would be ridiculous if you two are still living together. The guideline support formula presupposes you are not cohabitating and sharing equal responsibility for the children. (Meaning the children in your current relationship.)

Payment of child support for a new relationship is considered a hardship deduction when calculating child support with your ex-wife. If this was not done for the support order that you are paying now, you should file an OSC for modification of child support as pointed out by Mr. McCormick.