There is not nearly enough information here to answer this question. The answer lies in the state's need for federal matching funds for child support enforcement along with the individual facts of each case. Here are two hypotheticals.

In the first hypothetical, the mother's other child does not know his father and derives no support from that father. The mother hooked up with a man who gave him a child, so the father now has two children to support. In this situation, if the mother petitions the family court for child support from the man, all she must do is allege that the man is the other child's "psychological father," and that the man now has two children to support legally. The family court will grant the mother her petition and enter an order of support for two children against the man. Another thing mother can say is "paternity by estoppel," which is a lawyerly way of saying the man cannot say he did not owe a duty of support for another man's child he ended up raising.

In the second hypothetical, the other child has a visiting father who pays the mother child support, both visitation and support entered by family court order. The mother gives her new boyfriend a child. Here, the boyfriend will only be required to support one child because the other child is supported by another man. The state gets a greater matching fund for child support enforcement when more than one man supports more than one child. For example, one man paying 25% for two kids is less than two men each paying 17% (a total of 34%) for two children assuming their incomes are equal or their incomes are imputed to the same level.

There can be other variations to these hypotheticals which may better apply to this asker. The asker should see an attorney to see which hypothetical applies to him. The incentive here unfortunately is to avoid women with children because of the risks that child support and its enforcement brings to a man.