which full Cylon child?
You have Hera (I never quite understood if it's Caprica 6 + Baltar's or Athena + Halo's?) which is Human/Cylon and Tyrol + Cally's kid, which is also Human/Cylon.
Yes, I noted that too. I guess that will later point to other differences between the seven known cylons and the final five. Haven't gotten there yet. I'm pretty sure Tyrol's son will also be significant, but except for Hera, the others have been left in the background so far.
And about the final cylon, D'Anna says four are in the fleet. However, then only humans she has seen at the time she says so are Helo - whom we know is not a cylon - and Roslin. And she did ask Roslin if she knew she was a cylon, didn't she? And come to think of it, didn't Roslin act confused as if she blacked out for a second when the fleet jumped to the nebula at the end of season three, when Tigh, Tyrol, Tory and Anders found out they were cylons. Then again, there is evidence to contradict that as well, assuming Moore has been consistent and known who the final cylon was.
How can we know Helo is not a Cylon?