They're all a pretty confidential cast compared to other shows, but I would say Hilarie because she's the only one with out a twitter, we didn't hear about her divorse until way after it happened, same thing with her baby and realationship with JDM. And we only saw like two pictures of her kid and I think it was by accident. I actually think its pretty impressive that she's so private.

By far. She managed to hide her whole freaking pregnancy, for crying out loud! lol I didn't even know that was possible :P ...then once we found out that she did have a baby, she wouldn't even release what the baby's name was. So yes, I think it's fair to say that Hil is SUPER private when it comes to her personal life.

Plus she doesn't have any of the personal social media that the rest of the cast has either (twitter, facebook, blogs, etc.)

Definitely James.
I don't know anything about his life. I also don't go out of my way to find out anything about his life, but I don't do that with any of the cast members. I don't follow James on twitter, so maybe he has tweeted personal things...but I really don't know ANYTHING about his personal life (the only thing I have heard was that he dated Sophia for a little bit of time, and even then they never went to events together and if they were ever seen together it was from paparazzi pictures).

All the rest have publicly spoken about their husbands/fiances/girlfriends/boyfriends/ki­ds/­fam­ili­es (...etc.) and have taken their significant other as their date for red carpet events.
Hilarie would definitely be my 2nd choice b/c she is more private than the others, but she is still somewhat open about her private life since I know stuff about her private life (and I don't go researching her life)- she has posed publicly with Jeffrey Dean Morgan on the red carpet numerous times which is how I even found out she's dating him and he's the father of her baby.

I'd say Joy might be the most open. She posts stuff on her blog about her daughter, she talks about her family and friends, openly spoke about her husband, and now (somewhat) openly talks about her divorce. She's not so open about her private life, but I think she's more open than the rest. But Sophia & Chad definitely have their moments when they share a lot also.

I guess

by far,she hide a baby boy for three months guys:D

I didn't even know she was divorced until I found out that she was pregnant with Jeffrey Dean Morgan's baby.