No no no! OK, let me explain.
You know where it has all the lifetime wishes and it has links to the walkthroughs, read the description for Surrounded by Family. Carl says you can't adopt babies. He made a mistake, you can adopt babies and you can adopt them for the lifetime wish. I think he was under the impression that you couldn't.
And I'm pretty sure you can have a same-gender couple achieve the lifetime wish by adoption. Sorry, I didn't properly explain myself before.