If a 13 month old weighs only 13lbs, could he have developmental delays?

My daughter is 8 months, about 19 lbs, she is crawling, standing, babbling since 6 months however my nephew is nearly 13 months old, only 13 lbs and just recently starting crawling last month but still no babbling. He’s very calm, almost like he has no energy he just sits there all day. I’m worried for him that he may be developmentally delayed? They are looking into his weight now since he’s way under what he is supposed to be. Could his weight impact his development?

Edit: his mom is a vegetarian but mostly eats canned food, so I’m not sure what she feeds the kids but her 3 yo is and always has been a healthy weight. He is being brought to a children’s hospital regarding his weight.