The Ugly Betty star, who has 13-month old girls Charlie and Dolly with husband Jerry O'Connell, says that each of them takes after a different parent.
Romijn told People magazine: "Dolly looks exactly how I looked as a baby and Charlie looks exactly how Jerry looked as a baby.
"Charlie personality-wise doesn't take after anyone. She's really easy going and always smiling, doesn't cry very much. I don't think either of us are that easy going... I mean we're fun but we're not that easy going!"
Talking about doing a recent photoshoot with the children, the actress said: "I think Jerry was probably doing cartwheels behind the photographer trying to get them to calm down. Charlie was loving it - loving the lights, loving everyone standing around looking at her."