Maxperson
Morkus from Orkus
It's announced to Yoda, Bail Organa, and Obi-Wan Kenobi, by a medical droid examining Padme for the first time. Padme herself is not in the scene.
It is unlikely that Padme didn't know she was carrying twins. That doesn't apply to anyone else.
It's announced to two of the most powerful Jedi masters who can sense life forces... Do you really think that dozens of Jedi masters, including Anakin, all failed to detect twins?