omis1105 beutifully said, however I would like to correct one small point.
The general rule is that a toeiva partnership cannot properly raise a child this is a fact. For numerous reasons it is crucial to a childs development that he have the combination of a mother and father, not two mothers or two fathers.
And to ansewer the obvious question , No a man cannot properly asssume the role of a women just as a women cannot assume the role of a man (incidentally this is one of the grave errors in the feminist movement and is a leading cause of the breakdown of the modern family unit, but thats a different topic).
Yes of course I am sure there are isolated exceptions just as there are exceptions to every rule.
The thing we must realize is that the Torah is the blueprint of the world, the world is created from the words of the Torah (as explained by Rashi in Parshas Bereshis) and therefore the world can only run normally as long as it follows the laws of the Torah.