Two consenting adults, including relatives?

[Esquilax]

What about teenagers?
If gay teens in schools ought to be allowed to freely express their 'born-that-way' sexual preferences, then why can't they give consent to have sex... err... I mean express their Equal Love... err... I mean get legally married so people will stop discriminating against them?

When I talked about children equipped to deal with some form of freedom, I was talking about teenagers.

As to your questions here, the answer to the first one is the same as the answer would be for a straight teen; nobody is denying that teenagers have sexual orientations, nor that they have sex. The issue is that they still aren't developed to a stage where they can make informed decisions. So, while gay teens don't deserve to be messed with for being gay, any more than straight teens should for being straight, they're still in a position where their ability to make life choices requires some restrictions. Incidentally, the age of consent where I am is sixteen.

There's no double standard here; we occasionally have to draw lines, and changing those doesn't mean that we have to allow everything. In fact, I'd say that the lines for age restrictions on marriage, drawn in part from actual observations about human biology and growth, are more well grounded than the ones you're seeking to preserve about homosexuality, being based as they are in magic and the commandments of a space wizard.