I have a half-sibling who took one of those tests not knowing his parents went to a sperm bank due to fertility issues, so he assumed his mom had an affair (and he’s not the youngest child). The rest of us all knew I think (except the sperm donor’s actual child). Fortunately, he had another one of my half-siblings reach out to him to explain it.

Also “Turned out my father isn’t my real dad” is BS. Genetic test results are useless for determining such.

Genetic tests can be used to determine paternity though?

en.wikipedia.org/wiki/DNA_paternity_testing

Maybe you are referring to a specific type of test?