There is a widespread belief that there are adverse effects on children reared in same-sex-parents households compared to male+female household (I can add random googled cites if necessary, but the existence of laws preventing homosexuals to adopt should be enough evidence for that belief).
The effects could be either from absence of one of the sexes, OR from having "extra same sex parent".
Leaving aside non-scientific (though sometimes true) anecdotal responses that some M+F parents are worse for the child being reared than a well-motivated and caring M+M/F+F couple, my question is:
Is there any valid scientific study (preferably long term) that verifies the effects on the children of having two-male or two-female parent household (compared to 100% identical otherwise M+F household, and/or single-parent one). I'm looking for things such as, for example:
Sexual behavior differences (e.g. early sexual activity, risky sexual behavior etc..). I would lump in "rates of homosexuality" into this - assuming Kinsey graduated scale (as opposed to simpleton gay/straight), it's possible that kids who are biologically Kinseyity-X% gay would be more likely to act on that than those from straight households.
Rate of relationships/marriage for straight offspring of same gender (in other words, proof of common belief that having a father figure is essential for a daughter to be able to establish healthy relationships with males later in life)
I'm thinking a good study to that effect would include control groups from both 2-straight-parents households, same-sex ones as well as single-parent.
What I'm looking for is whether there are any studies that, correcting for other sources of variation, exibit systemic differences (or lack thereof) in offspring that are similar between F+F household and single-mother one, e.g. stem from a lack of father (as opposed to having a second mother).
Or studies that are vice versa, showing that there are differences (or lack thereof) between same-sex-romantic-partner household reared children compared to same-sex-non-romantic-partners ones (e.g. a child reared by lesbian parents vs a mother and an aunt)
P.S. As a background, a lot of people I know (myself included) have only ONE criteria for deciding whether to support things like gay marriage/gay adoption etc...: what does science say on the matter of "gay child rearing"