I've seen here on PPD several times women parrying paternity test discussions with notion of "parallel families" - i.e. married men having and raising children with their mistresses and supporting them financially. I could not find a single scientific paper investigating this phenomenon. Apparently such behavior has never been even attempted to prosecute under monogamy laws (all court cases on monogamy I could find were members of religious communities demanding being allowed to have several spouses; many of the plaintiffs women).

While Yes, many men nowadays engage in extramarital sex, and many happen to have "oopsie babies" sometimes, I couldn't find any evidence pointing out what share of these men is married and bleeding their resources into raising the illegitimate child.

Meanwhile, we have at least one meta-study investigating rates of non-paternity events not only among general population, but also a "relatively high confidence" subset of it. https://www.researchgate.net/figure/Nonpaternity-Rates-When-Paternity-Confidence-Is-Relatively-High_tbl1_246396004

If there is no estimate of how common "parallel families" are, I think it's safe to consider this scenario a purely hypothetical, made-up "gotcha".

Discuss!!!