Rebecca Romijn's Perfect Family Of Four

It sounds like two is enough for Rebecca Romijn and Jerry O’Connell.

The model mom, who welcomed twins Charlie and Dolly last December, tells E! that she and her hubby are happy with their family of four, saying, "I'm pretty sure that this is it. We feel like the world was made for pairs. Four feels like the perfect number."

Rebecca adds that their decision not to expand their family further was also made with sustainability in mind: “We're not interested in overpopulating this world. So we feel like we don't want to leave more than we are when we leave this planet."

As a working mom – Jerry has been staying home with the girls while she films the new series, Eastwick – Rebecca admits she feels some Mommy guilt about missing out on time with her babies.

"Mother's guilt is no joke," the Ugly Betty star says. "I feel like any stretch of time I spend away from them, I'm worried that I'm missing out on just these little miracles. Like you watch them stare at their hand for an hour and they go take a three-hour nap and they wake up and they can do something that they didn't do before—like wave!"