Their reaction to you being pregnant.

Dean:
Dean was horrified. He didn't know if he'd be a good father or not. Dean knew he'd have to stop hunting for a while.

Sam:
Sam was thrilled. His lifelong dream of settling down and having a kid, but he never thought had have that.

Castiel:
Cas told you before you even knew. He was going to be good father, he just hoped he wouldn't be like his father.

Adam:
Adam was ecstatic. He was thrilled to finally get to be a father, and he vowed never to leave you or the baby like his dad did with him.