Maggie Gallagher's Meaning of Marriage essay points out that in all but one of the subfields of research on parenting, there is a growing scholarly consensus that kids benefit most when they are raised by their own married father and mother. The one genre of parenting research that says otherwise is the research on homosexual parents.
The big claim made about the homosexual parenting research is that kids do just fine when raised by homosexual parents and same-sex couples. However, Gallagher cites Steven Nock's comprehensive review of the literature, which concludes that "all of the articles I reviewed contained at least one fatal flaw of design or execution."
One big hole in the whole body of gay parenting studies is that none (or maybe one) uses a nationally representative sample – a norm in family studies otherwise. Another big hole is that most of the gay parenting studies have been done by psychologists looking at gender identity and self esteem – important questions, but not like the range of economic, medical, academic, criminal, attitudinal, and behavioral measures that social science routinely asks about families. The psychological studies have found that children of homosexual parents are no more likely to be homosexual themselves than are other kids. It is a long way from that finding, though, to a conclusion that children of homosexual parents are no different from other kids across the board.
Lately, the major policy concern has been about same-sex marriage. The "no difference in the kids" claim has been applied to this debate, too. Yet one of Nock's important findings was that the vast majority of the studies of homosexual parents have been about lesbian single mothers. It is not so surprising that the children of homosexual single mothers are not that different from the children of heterosexual single mothers. But that is a long way from showing that the children of same-sex couples turn out the same as the children of their own married parents.
Gallagher can not answer the big question – do children of same-sex couples turn out the same as children of their married parents? – because there is almost no research on same-sex couples raising kids over time. And obviously, since the possibility of same-sex marriage has only existed for a few years anywhere, there is no research on the effect of same-sex married couples on their kids.
Gallagher expects that when such research is done, children of their own married parents will still do better. She thinks this because two biological parents still invest more in their own kids than one parent and a step-parent. Moreover, men and women, as a rule, are different, and children generally benefit from having both kinds of parents. Those lesbians couples which have done the best in raising boys, which I wrote about earlier, went out of their way to involve men as role models in their sons' lives.
Few researchers expect that same-sex couples will turn out to be bad parents. But it is very premature to conclude that their kids turn out the same in all respects as children of married parents.