I had one boy here long time ago sound similar. He was premature birth but only 5 or so week and parent used as reason for be behind. He barely sit up at one year when come for interview. Sweet nature boy but not crawl, speak, walk, or make any attempt. Not even lift arm for pick up which even small children do. I not like use term "bump on log" but it most descriptive for this child.

As time pass I learn that they live in apartment and so no stair which why even when he did start crawl, he not know how use stair. I also learn grandparent look after him before and they over protective and no let him do much for fear he get hurt.

It was lot work. He used to be in room filled with crazy amount toy at home and parent pass him anything he glance at. He never need speak or move to get something himself.

I spend long time getting him walk. Even other children would take his hand and lead up and down hallway. Parent tell me one day that he trip at apartment and then grandmother not let him walk any more but she carry him.

Took lot of conversation with parent to explain that new skill take time to master but more we practice anything, better we get. That he will stumble and fall initially but he will build strength in muscle more he does and that also help make more stable.

I think, because he little early and parent have big scare of uncertain time, that they were very frighten of something happen to him so they made sure to wrap him in bubble. I think they mean well but likely make situation harder. It took about 8 month to get him feeding self, crawling then walking, talking with parent, and lot encouragement but did catch up in end. Then parent leave because child care too expensive and boy go back to grandparent each day.