PS: The point here is NOT that poor people shouldn't have kids, it's that no one should be having kids without having the basics of childcare covered, which necessitates widespread systemic, societal, and economic change so that no parent needs to worry about those basics, and kids can grow up in secure, healthy environments. I completely forgot to mention this when I originally posted it, and that's my bad.
Most people have something like 7-12 genetic defects. (AI says my view of this is technically imprecise, but I don't want to paste the entire analysis.) My guess is you don't notice any of the defects and if the older one has slightly more they are also not noticeable. Defects don't have to be completely destructive. Like for example, in protein folding, shape determines a lot, but like you can have a protein that's slightly off in the fold that may functionally mostly work the same, but maybe it results in more problems if someone has a kidney infection. In other words, it's not always obvious or debilitating?