I think a child has a right to have both a mother and a father, as nature intended. But there are many children who only have one parent, or no at all, or who have parents who are mean to them. Two loving parents of the same sex is probably better than those.
When it just comes to letting them be together and marry and stuff, I'm not the one to stand in their way. The love between two people should only concern the two of them alone and is beautiful no matter what genders are involved.
That being said, I have some gay friends who are in relationships and I tend to be a bit... well, uncomfortable when they talk about them being together and, you know, doing it. I guess it's either society that has made me feel that way, or the fact that I definitely wouldn't like to do something sexual with a person of the same sex as myself.
if you were fantasizing about that, too bad 8D