Dude, googling the name of that study returns commentary on the problems. Among them:

"Sullins achieves this through a crucial elision between households in which a child spent some time in a home headed by a same-sex couple and families in which a child was actually raised, from birth, by a stable same-sex couple, a situation more auspicious for healthy child development. This conflation of household stability with parent gender fatally mars his conclusions, which are much more damning of gay and lesbian parenting than are warranted by his data.

Sullins claims that his study examines “children raised by same-sex parents into early adulthood.” But in fact, he has zero basis to draw this conclusion, as he is applying a wholly untenable definition of “raised by.” All he knows about his dataset is that his subjects, who ranged in age from 12 to 18, spent some of their teenage years with a parent who at some point had a same-sex partner. Since we do not know if that partner was ever actually a parent, legally or otherwise, it is inaccurate to characterize such households as “same-sex parented” as Sullins does eleven times.

Not only is there no basis to conclude that these subjects were raised by same-sex parents, but also there is every reason to believe they likely were not.

This descriptor, of course, is the key variable in the discourse on optimal child-rearing because of the well-established fact that children who experience divorce or other family disruptions are at higher risk for a number of disadvantages, including the ones that Sullins inaccurately associates with “same-sex parented” households."

So the guy doesn't even clearly establish that these kids were raised by same-sex couples, and also lumps in children with other problems such as a divorce and/or change in parents, which themselves are known to be contributing factors to a sub-optimal childhood.

Also, his agenda is clear. The guy is a Catholic Priest that works for the Family Research Council, which believes, in their own words, that "Homosexual conduct is harmful to the persons who engage in it as it is associated with negative physical and psychological health effects. Thus, it is also harmful to society at large."

Finally, the study was published in a pay-to-publish journal. I am aware that there is currently a leftist bias in academia that would make it hard to get this published in leftist journals even if it could pass any kind of real peer-review, but it doesn't matter because it can't anyways. You can't mix stuff like divorce and change of parents in and expect that to not have a significant impact on the results. That's ignoring the fact that the agenda of a Catholic Priest working for the family research council is clear. I'd trust a "study" from them on gay issues about as much as I'd trust a "study" from a transgender person who works at a gender clinic claiming detransitioners barely exist. By the way that comparison was because such a study written by trans people does exist, and it is also fatally flawed.