Hi, So I Have Cousins And They Both Have Really

Hi,
So i have cousins and they both have really big skull, small face, bulging eyes, ALMOST normal mouth if not smaller, and is very short in height. Yet, she talks normally as an 8 yr old would but also has a very smart mouth. Her borther i s just a month and a half and seems normal when he looks around as a new born does. i have attached a photo of the 8 yr old to show exactly the height and other features. Please explain what this is and what causes it. Thank you.