Re: There is no data justification
Women can have kids wth donated eggs so zero genetic link there.
Adoption - zero genetic link, but parent(s) are legally resposnible for that child.
If someone marries a person who has young kids they typically accept their share of legal rfesponsibility for those unrelated kids.
So, DNA often irrelevant, thus it was discriminatory (not even going into areas of 2 men having kid via surrogate to add more complex example's of zero mother)