Max passengers in a soft sleeper room

Is there a maximum number allowed to sleep in a soft sleeper cabin on Chongqing to Kunming train? I know there are four bunks in each cabin and our family consists of six people(two children under 120cm, two under 150cm and two adults). Since two kids are under 120cm and "free" with paying adult, the two youngest can bunk with their older siblings and the two adults take the top bunks. Will they have a problem with us doing that?