How can support be order after 12 years of dening I am the father? Another man took that responsibility after I was told I was not the father. The bad thing about it is this woman may have been on the system, will I have to pay all that too? I am requesting a paternity test ASAP!

Depends on your state, in most, it does not matter how long it takes to prove, if you are proved by DNA to be the father, yes they can collect back child support and yes the state will come after for money from where the child collected welfare. ( this is where they really hunt the father down, when the state wants their money)
The other man may have been tested and may not be.

Denying you're the father is not enough... You have to prove that your not the father. Maybe another man took responsibility for a period then decided he wanted tests... could have proven he was not the father. Now your being looked at. It's unfair that the mother didn't get this issue resolved much closer to the child being born however she didn't and the "state" wants to be reimbursed. They don't care who does the reimbursing. You could be ordered to pay support for an interim (until paternity is proven), you could be ordered to pay in absentia (even though your not present as you were notified?), or you could be ordered to pay as there is more evidence that you are the father than evidence that your not. Basically, you need to contact child support enforcement and request paternity tests... in writing. Not just verbally. To speed things up you could have course get an attorney. I want to say for women everywhere... I don't agree with not having a father know he is in fact a father. Men have rights and some women have absolutely no respect for that fact. I'm truly sorry you weren't given the chance to be a father from birth forward if you are in fact the father. Run don't walk to child support/attorney to get this issue settled. Cathy