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If the children are still under the age of 18 then yes you can take him for child support. The chances of getting back child support (Or getting the support retroactive) is slim but a possibility. The age of the father is of no issue in child support regulations.
Your first step is to go to your local Child Support Enforcement Agency and asking for services. This is normally free but if your income is high they may request a 25.00 fee.
They will give you a packet to fill out you can give them his social security number and any other information you have. As for the address while this is helpful it is not a must have thing. They can track him though his social security number. Fill the packet out and return it. They will get in touch with him and set up a hearing to establish support amounts and then the judge will court order it. At which time they can either garnish his wages or allow him to pay by check (Garnishment is much more common).
They will then send the money to you each month in the form of a check or though a child support debut card.
It is not difficult and they can help you.