 When the Camden twin boys Sam and David were introduced to the show  in the middle of season three the "7th Heaven" crew used quadruplets  (Zachary Brino (qv), Lorenzo Brino (qv), Nikolas Brino (qv),  and Myrinda Brino (qv)) to play the twin babies as they rotated  them around between scenes due to Child Labor Laws and the amount of  time one set babies could be kept under lights and camera. But as  the twin characters became older the producers decided on using one  pair of the quadruplets, Lorenzo and Nikolas, especially since one  of the quadruplets was a girl. Beginning from season six both boys  had the roles permanently of Sam and David Camden and then appearing  in the opening credits of the show.