The 39-year-old star, who has 15-month old twins Max and Emme with her husband Marc Anthony, can't believe how little her kids have in common.

She said: "It's like night and day. It's like, this is little man, this is little woman.

"She's very delicate and precise and careful not to fall, and he's just barrelling through everything, screaming and eating everything he can get his hands on."

Jennifer also revealed she was so amazed when she fell pregnant it took her a while to register the happy news, while Marc immediately started crying.

She said: "At a certain point, you start to think, 'oh, maybe this isn't going to happen for me.

"Then, when I was about seven weeks, the doctor said, 'oh there's a little heartbeat. Oh there's another little heartbeat. I was like, 'oh God!' I just laughed. Mark cried, I laughed. I was like, 'of course. Why not?"