If the state failed to notify the man, and provide the paternity testing before they declared him the legal father they screwed up but it took this guy an awful long time to decide it was time to resolve the issue.
Personally I think this guy basically ignored the problem until it got out of control, and that's what happens with a lot of support cases, people don't tell the judge their income is reduced, they don't show up for court, they ignore notices.. and then they are shocked by the outcome.
My son has a friend who is still legally married - his wife and he have a daughter, he pays support and is a good dad, but he insists that since she kicked him out she should initiate and pay for the divorce.. meanwhile she's pregnant again, by her current boyfriend.. everyone keeps telling him he better get that divorce or he's legally dad to this baby as well. He waves everyone off but if he doesn't follow through legally to insure that the child is NOT considered his... he's looking at a long term financial mess.