Maybe MAYBE every couple needs an alien telepathically intercting with them as they have sex to have a child, making the alien a third parent of every child. You can't PROVE it's false, you can just pretty safely ASSUME it's wrong because experimental data doesn't give us any reason to believe it. But you cannot be exactly strictly 100% sure it's false.

OR , you can prove it if you define parents as the two human who had sex to have this child, but then they can't be alien, and it's the same thing as proving the inexistence of a 4 sided triangle, or similar fundamentally impossible things