Social Security and Child Support?

You seem to be asking about two different things - first, you say child support is being taken out of your monthly benefit and then you ask if a second case comes up will they take money out for two cases. Monthly payments and back payments are treated differently in the case of someone receiving SSI benefits.
SUPPLEMENTAL SECURITY INCOME (SSI)
SSI is a government benefit paid to the elderly and disabled. It is for people who have not earned enough in the past to get Social Security Disability (SSD). SSI pays a set monthly amount.

First question - Be sure you have been approved for SSI benefits and not SSD or SSDI as these are handled entirely different with Social Security laws/rules.

Some states handle SSI benefits as income and that means there is a possibility that support payments cannot be suspended - even through the court. I know that Florida and Ohio are 2 states that make people claim SSI benefits as income.

When SSI benefits are approved there will generally be a check issued for the monthly payments from the time period when case started and date approved. This could be for several months (or years). If back support is owed that SS check can be garnished by the guardian of the child/children but they have to get a court order or apply to SS before the check is issued.

If a person is behind on support payments to more than one family then that second family/person can also apply for a cut of that SS check. Proof of amount owed has to be presented to the court/Social Security for payment before the check is issued.

These garnishments of the check cannot take but a part payment of the check and sometimes if two families apply for payment of back support it will reduce the amount that only one would have received. SS and the court would have to make those decisions about how much each would receive (you, 1st family, 2nd family) as it would be based somewhat on the total amount of back support due each family.

Here are some excerpts from a SS attorney: Can My Back Pay Be Garnished?

"If you are entitled to a lump sum of back pay and you owe past-due child support, your back pay can be garnished to satisfy this debt. While your entire back payment will not be taken from you, a percentage of it may be garnished in order to fulfill your child support obligation.

Parents who get SSI cannot be forced to pay child support. Parents who get SSD might be ordered to pay child support.
If a parent's only income is SSI, that parent cannot be forced to pay child support. Some courts may still enter a child support order, but will not enforce that order. The Child Support Guidelines specifically say that SSI is not counted as income on the child support worksheet. By definition, someone who is getting SSI is unable to work because to be eligible for SSI you must be unable to work.

If you are the parent getting SSI, you should tell the court that your only income is SSI and you are unable to pay child support. You should get a statement from the Social Security Administration that you receive SSI, and give this statement to the court. If you have already been ordered to pay child support and then you began receiving SSI, you can ask the court to change your child support order."

Because SSI is considered a welfare benefitrather than an earned Social Security benefit like retirement, disability, or survivor benefits, which individuals pay into over their lifetimesthe federal government does not allow this income to be garnished for child support payments, says Vicki Turetsky, commissioner for the Office of Child Support Enforcement.

If you are awarded SSI, your benefits cannot be garnished to make child support payments but your back benefit check usually can.

You should pay a visit to your local SS office and find out what yours and your children's future holds as this is always a complicated matter and once payment is made there is usually nothing that can be done to correct it.

This does not mean you are no longer responsible for child support, it just means that SS has found you disabled/unable to work and the (low) monthly check you will receive is not counted as income.