Say you live together with a woman.

Unknown to you, the woman becomes pregnant by someone else.

From the beginning you already said that you only want to be responsible for your own children.

Now, after the child is born you quickly do a paternity test, which shows that the child is not yours.

Under what jurisdiction do you have to pay child support anyway?

  • That will depend on whether you are married to that woman and whether (once you found you are not the father) officially deny that.
    – PMF
    May 6, 2022 at 8:55
  • 2
    @PMF from "gf" in the title I think we can assume that no marriage exists.
    – phoog
    May 6, 2022 at 9:49
  • I would never get married. I am not that stupid
    – obfuscated
    May 7, 2022 at 10:01

3 Answers 3


In the United States, man's obligations to pay child support for a child, is based upon a determination of the paternity of the child.

Paternity, once established, gives rise to multiple rights and obligations, and not merely to an obligation to pay child support.

Paternity determinations are questions of state law for most purposes, including child support, and U.S. states are not entirely uniform on this point. However, state law is only advisory for select purposes of federal law, such as citizenship, which ultimately, for that purpose, is a question of federal law.

In California, in a case involving an unmarried woman and an unmarried man, when there is no putative but legally invalid marriage, but they cohabit, there is only one circumstance where a man is presumed to a parent in the absence of court action or an acknowledgement of paternity, under Family Code § 7611. This is a man "who receives the child into his or her home and openly holds out the child as his or her natural child." Family Code § 7611(d). Both of those requirements must be met for the presumption to apply.

When this presumption does not apply, paternity can be established affirmatively in a paternity action, which typically is resolved with a DNA test, or with a voluntary acknowledgement of paternity in a suitable document.

  • So if a rich guy like a woman that already have a child, and take care of them both, he can be liable for more liability. Interesting.
    – obfuscated
    May 7, 2022 at 10:04
  • @obfuscated Only if he "openly holds out the child as his or her natural child" which would not be the norm in that fact pattern.
    – ohwilleke
    May 7, 2022 at 18:17

(jurisdiction: )

In case you are married to that woman, the state assumes by default that it's your child. In case you are not married, you can accept paternity by declaring so. Either of this is independent of whether it is actually your child or not, the law was written long before paternity tests where commonly available. If you accept paternity or if the law assumes it's your child (and you do nothing about it), you obviously have to pay.

If you contest paternity, you can do so. The law is complex here and has different assumptions about whether you where married to that woman at some point and whether the child could have been procreated within that period etc, all of which is quite obsolete with todays possibilities.

So, if you have (successfully) contested paternity, you would not normally need to pay (but the real father has to).

The law is not very distinctive about some border line cases, like when you life with that woman and heir child in a common household and the real father doesn't/cannot pay and the child's wealth is at stake. Then a judge may assume that you "inoffically" adopted the child.

  • So, even if I have no intention to adopt a child a judge can declare that I adopt it? WTH. So stay away from women with a child then.
    – obfuscated
    May 7, 2022 at 10:02
  • 1
    @obfuscated The law is vague, but I just read a commentary that confirms my writing above. And it makes sense: If you live with that woman and heir child (and eventually even marry her later), it would be ridiculous to deny any responsibility for the child.
    – PMF
    May 7, 2022 at 11:23
  • I think it's very obvious to me that almost no men would financially be responsible for someone else' children unless he is tricked or forced into it. For example, say a woman already have a child and I took care of her and her children. It's pretty obvious that my intent is to get sex from those woman and taking care of her child is what I do to get pussy.
    – obfuscated
    May 7, 2022 at 15:31
  • 1
    Love is not only about sex. It's about caring for each other. If you want her to love you but you actively ignore her child, I don't think that will become a good relationship.
    – PMF
    May 7, 2022 at 16:12
  • I don't love children that are not my children.
    – obfuscated
    May 17, 2022 at 5:32

If you cohabited with the mother for 10 months prior to the birth you are presumed to be the father:

Ordinarily the paternity of a child is acknowledged by both parties. The court will in these circumstances presume paternity Family Law Act 1975 (Cth) s 69R. A man is assumed to be a child's father if the man:

  • was married to and living with the child's mother when the child was born [s 69P]
  • has signed a document acknowledging he is the child's father (and has not rescinded it) [s 69Q]
  • cohabited with the child's mother in the ten months before the child was born [s 69R]
  • is acknowledged on the child's birth certificate as the father [s 69T]

The court does not order DNA testing alone. This can only be done as an ancillary procedure to a parenting application. Thus, orders for DNA testing cannot be made simply to satisfy the curiosity of a parent. They will only be ordered where they are needed in order to determine whether any parenting application is in the best interests of the child concerned.

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