If I already have a boy, and I'm having another child which I don't yet know the gender, the chances of it being a boy are 50/50. This is essentially the situation described: guess the gender of one person.
I'm saying that IF you want to consider the order that the children are born in, and that order is unknown, we get the following pattern:
Plug your possible values into the above template and you get:
If your going to count the known male twice in one scenario (a know male and a female) why wouldn't you count it twice in the other (a known male and a male).
You really have to be careful to be consistent. Either order matters or it doesn't.
If no order matters, it male-male vs male- female. Other wise it's known-male-female and female-known-male vs known-male-male and male-known-male. You can't half ass it. It's one or the other.