@Val Killmore,
You are claiming the gay marriage argument is bad because it doesn't cover all scenarios you consider bad. But then your own argument doesn't cover all scenarios.
Do you think a brother and sister should be able to marry if they are over 60 and obviously can't have kids?
What about if they are in their 20s present evidence that they are incapable of having children?
Your "kids" argument is as silly as the rest of your arguments when we simply trot it down to the end of the lane like you attempted to do with the gay marriage argument.