Legal Question in Family Law in California

The answer to all of your questions would best be answered by you going to a family law facilitator and having a dissomaster run, with the appropriate figures, to determine whether an award of support would be made, and if so, how much.

First off, you don't mention whether or not the father has been legally declared the father. Unless he signed the statutory Declaration of Paternity, or there was a court order, he is not the legal father. Since support normally would have been set as part of a court proceeding, and there would have been a formal visitation order rather than the informal arrangement you describe, I assume there was not one. So until you establish paternity, you have a non-starter on the support issue.

Once and if paternity is established, Mr. Stone is right that inputting all the data into a Dissomaster run will tell you exactly what would be due if anything. Short of that, I can tell you that if the incomes are close to the same, but the custodial time is disproportionately with the higher earner, there probably would be some amount due from the lower earner non-custodial parent to the higher-earner custodial parent. The step dad's income goes into the Dissomaster program, but only to reflect it's impact on the taxes and deductions on the mom's income. One of the great unfairnesses in the CA child support system is that when a parent remarries, they get the benefit of a second income without it counting for support, but because it may increase their marginal tax rate, they might wind up paying less support if they pay, and getting more if they are the receiving parent. If the paternity has already been legally established, the court has the power but is not required to go back up to three years for back-support. If the support request is at the same time as a paternity proceeding, then it can only be from the date of filing forward.

One last thing I should mention is that if you don't already have paternity established and a custody order, which it sounds like you do not, custody as well as support will be in issue. There is a public policy that favors 50/50 physical custody or as close to that as the life circumstances of both parents and the child permit. So bear in mind that you will be opening that can of worms if and when you file for paternity and/or support. If the father asks for it, he is likely to get a lot more custodial time than he has now, up to 50%, theoretically more if he an prove primary custody to him would be in the best interests of the child.