There are two issues here. The first is the fact that your daughter receives a SS check because the father is disabled. The second question is the amount of child support that he is ordered to pay. At the time that the child support was ordered the father may have been working and therefore receiving more money but now that he is not working he is not able to pay as much. In Florida where I practice I tell clients that the amount of SS benefit that the child receives will be considered a credit by the Family Law Judge but that alone may not completely satisfy the child support obligation. I also tell the non-disabled parent that a modification of the child support obligation may be in their future. I hope that this helps.
This information is provided as a public service to provide a general answer and should not be relied upon as legal advice.
The SS dependent check you receive for your daughter "may" satisfy his child support obligations. It is up to the Child Support Judge to decide this. It the disability is his only income then the SS dependent check you receive may very well be considered enough to satisfy his obligation. You need to talk to a family law lawyer in your state.
This response is meant to be information only and should not be considered to be legal advice. This information is not meant and should not be construed to be the formation of an attorney client relationship. I practice Virginia Workers compensation law and Social Security Disability law.