Victims of rape should clearly not have to pay child support for the offspring of the crime. However, this is not the case in the current US legal system.
One example from 1996 is the case of Nathaniel J., who was 15 when he had sex with a 34 year-old woman. The woman was convicted of unlawful sex with a minor. Nathaniel was billed for child support; he appealed, of course. The Court of Appeals of California ruled against him, saying that he was a "willing participant" in the crime. (San Luis Obispo County v. Nathaniel J.)
There are several more cases like this, for example Hermesmann v. Seyer (1991).
I find this surreal and deeply unsettling. Please join me in saying that the above doesn't make sense.