I need to know what steps to take,I know someone that is working under 2 different ss#'s and has 2 kids her in the us that he don't have living with him but he is getting child suport for them,he also is getting food stamps for them. He also has claimed his 2 kids that are in mexico on many different things to get more help for himself from the state.. This is very wrong when we have people working hard and can't make it to take care of there kids.

Report suspicious activity to I-866-DHS-2-ICE. Have detailed information and provide your contact information. Please note that unless there is suspicion of criminal activity, the US ICE is not likely to investigate.

Report medicare and food stamp fraud to that specific agency.

But also don't expect immigration to get too concerned if he is not considered a threat, merely being a non dangerous criminal is not going to even get them interested.

Example here in GA, we had several illegal do a protect, proclaim publicly they were illegal, do a protest, block traffic and refuse orders of police officer, immigration basically said they were not interested in them since they were not dangerous.