choice
the idea of marrge is one of the fundamental pillars of any society, a household composed of two or more people who all ake care of each other is the basic building block of any culture. in some places its bigger such as imperial china where the family was any relitive, or sometimes its smaller, such as now, when its usually just the imediate family. without this bbasic strcture, the larger structure of soceity colapses. look at any place that tried to rid itself of family, look at communist countries where whildren were raised communaly. did any of them survive? look even at the kibbutzes in israel, by far the most effective communistic soceitys there are. they too faced problems with communaly raising children, so they abolished the practise.
a single person is not a family, and our society should not have laws to encourage it because it does not add to the overall stability of society. an inersex couple without children qualifies for some benifits, just the same as a gay couple. single parents should qualify for more, but a single person does not since he does not add to the stability of the basic unit of society.
equality does not mean that every single person is exactly the same, as you seem to think it does, it means every person in hte same position is entitltes to the same rights and benifits.
that does not mean a dead person is equal to a live person, that does not mean a smart person is equal to a stupid one,