Yes, they should be able to, because how could you, in this day and age, deny gays the rights of raising children that:
- were born to them in straight relationships prior to their 'coming out'.
- were born to them in an agreement with outside donors
- were sort of assigned to them to be raised by a relative or close friend because these biological parents are either too ill or otherwise incapable of raising them
The discussion often centres on adoption, which I think has turned out to be the big issue, not primarily of gay vs. straight, but of stories that keep emerging of parents in mainly third-world countries or conditions of poverty and hardship who are either forced to or paid to give them up. They would be far better off, if there was proper monitoring and there would be enough funding to have them raised by their own families or relatives, in other words more local solutions than this 'baby trafficking' across the globe.
That's why I wouldn't normally want to adopt children, if I wasn't 100% sure of their origins or conditions.
Rich