I don't think that same sex marriage is a sin. It is not your fault if you fell in love with someone who has the same gender as you are.As long as both or each of you respect each other then that's good.
OK.. It is not a sin to love someone of the same gender (still I wouldn't consider it to be a normal thing). But what is the point in recognizing such relationships as marriage and then giving welfare payments and legal protection to these people? Homosexual couples can be tolerated. But they can never be given equal rights as the heterosexual couples.