Same-sex marriage removes biological identity
Yes, these are of central importance, but children also need identity, genealogy, healthy parental role models, and the support of the biological extended family, which includes grandparents, siblings and other blood relations.
Both the statistics and common experience attest that children fare best in life when they know who they came from, have a belonging that is both cultural and biological, grow up with a model of married life that is a reference for their own future relationships, and enjoy the support of the extended biological family.