There are two issues here. The only parents on a birth cert should be the biological parents. The biological mother and the biological father. And I guess in cases of a gestational surrogate with another woman's egg, that also needs to be recorded. A birth certificate is a factual document for the child and nobody's ego should come ahead of that. (I know it's easy to falsify who the father is, but we should be looking at using technology to make these certs more accurate. Not butchering them.)

The second issue is about legal parenting. In a same sex couple I have always felt the non-bio parent should be able to adopt the child so the family unit has legal protections. But I do think realistically, that needs to be restricted to two parents. We have to have boundaries somewhere. And our whole family legal system is based around two parents, as that is the norm. Custody issues, for example, are hard enough to deal with already. Adding a third legal parent to the mix, just creates a multitude of potential issues that make creating a fair situation for a child nigh on impossible. This is fucked up in two ways.