SCIENCE! That child cannot be made without the sperm, from one of the legally consenting adults. But thank you for providing evidence that it is unequal protection!
Actually, thanks to the science of cloning, we know that a child can be made without sperm, though the experiments haven't been done on humans yet.
But in addition, we know that many men with healthy bodies, high IQs, and good genes have donated their sperm to sperm banks. If a woman wants to get pregnant, she doesn't have to have sex with a guy. She can get sperm at a sperm bank. Or if she has a friend who would happily donate but not be a father, they can draw up a formal sperm donation agreement with no financial obligation of the guy.
You are making much too big a deal of pregnancy that relies on sexual intercourse. Furthermore, traditional Christian marriage was never about a man's relation to his biological kids. The point was that the man actually promised to love the woman and, forsaking all others, keep himself unto her. That doesn't just mean no sex with other women.
In the US, if you see your kid or your parent commit a crime, the government can force you to testify as a witness against him/her, as it can in all other cases except if the person is your spouse. That's because your spouse is your chosen best friend, and you got to choose her/him, whereas with parents and kids, everyone is taking pot luck. The point is that, in order to love your spouse above all others, you have to side with what it best for him/her, his/her life, health, bodily integrity, human dignity, etc.
If you're not capable of that, because you care more about the embryo you mistakenly contributed to in the woman when you had meaningless sex with her, why would she want you as a spouse?