access *to* the protected class is not equal

Excellent turn of phrase -- it's succinct and gets exactly the point across. Thanks.

A man can't divorce his cheating wife & claim "that kid's not mine;"

Wait, haven't there been paternity suits over exactly this?

Agreed, though, that it gets awfully thorny when same-sex couples are involved; surrogate mothers for the children of gay men usually surrender parental rights, and I think sperm donation works the same way.