Twins Merle and Stijn may not have clarified their ideas yet, but that doesn't mean they can't communicate.
The twins were panting for breath while their father was walking and decided to photograph them on the job. And picking them up in the middle of what appears to be a very reasonable conversation, is where many emotions are displayed.
Watch the video below to see Merle and Stijn interact with each other. It's really nice to watch them interact with each other. What do you think they say to each other?