A same sex couple can both have biological connections to the child by using genetic material from one, and from a close relative of one partner, if biological connection is important to both of them.<quoted text>
A ss couple cannot procreate a child.
Simply produce a legitimate study that equates a default couple with natural parents, including study methods.
You then still have the insurmountable problem of depriving a child of a father or mother.
Again, biological connection is no guarantee a child will not be denied a mother or a father or both, or that they will not be abused or killed. The nurturing quality of the relationship is the important variable. Adoption provides a child with two caring and motivated parents instead of having none.
The level of documentation you demand usually requires a fee for access to professional journals. Meanwhile, mainstream medical and mental health organizations agree with the American Academy of Pediatrics:
"Extensive data available from more than 30 years of research reveal that children raised by gay and lesbian parents have demonstrated resilience with regard to social, psychological, and sexual health despite economic and legal disparities and social stigma. Many studies have demonstrated that children's well-being is affected much more by their relationships with their parents, their parents' sense of competence and security, and the presence of social and economic support for the family than by the gender or the sexual orientation of their parents.
Lack of opportunity for same-gender couples to marry adds to families’ stress, which affects the health and welfare of all household members. Because marriage strengthens families and, in so doing, benefits children’s development, children should not be deprived of the opportunity for their parents to be married. Paths to parenthood that include assisted reproductive techniques, adoption, and foster parenting should focus on competency of the parents rather than their sexual orientation."
But all of this is about reproduction, adoption, and being good parents, not marriage, as raising children has never been a requirement for marriage to remain a fundamental right of the individual. Marriage provides benefits and protections for children, but none are required. Ability to have sex is not even a requirement.