That is a physical impossibility.
Their child can meet a birthparent who has a live-in boyfriend or girlfriend of the same sex.
Can same sex couples both put their names on adoption forms?
"Can same sex couples both put their names on adoption forms?"
Yes, in some states.
Here's some info on states which have allowed gay or lesbian partners to adopt children where both halves of the couple are legally parents. This is most common with lesbian couples where one partner has given birth to the child, and the other adopting as a second parent.
"That is a physical impossibility."
Not for long, it seems. Research is ongoing on ways to fertilize a woman's egg with another woman's genetic material. Similar research is ongoing to create a "male egg," which would be fertilized with another male's sperm.
In the first case, one of the women would carry the baby. In the other, a surrogate would be required.
Please note that I am not in favor of such, but it does appear that things are about to change. Right now, they're working with mice, but....
More info at:
http://news.bbc.co.uk/1/hi/health/1431489.stm
and
http://www.findarticles.com/p/articles/mi_m1589/is_2002_March_19/ai_83667580