We have twins, a girl and a boy. The girl is already sitting up, crawling, reaching out her hands, but the boy just lies there and doesn't move, gets upset if he's not turned over or sat up, and only sits if we place him. If you put him in a walker, he's already running away from us. He likes to stand on his legs, but doesn't do anything on his own. The neurologist said that at 9 months, they should be sitting up like mermaids at least and babbling syllables; otherwise, they'll prescribe some pills or injections. I'm worried because our 9-month mark is at the end of September.