Why doesn’t my stepson use his words

My 3 yr old stepson is with me and my bf at least every other week. He cries and whines when he’s told no, when he is told not right now, when he is told in a minute. He cries and wines until he gets his way. He whines and cries literally about everything. I have did research online and has had a talk With his father and we have tried explaining to him that whining doesn’t work and we will not respond to the whining and crying. We also told him to use his words and to act like a big boy and we don’t understand whining and crying. He still chooses to whine and cry about literally everything. I get the idea that he doesn’t know how to express himself other than whining or crying but we have tried explaining it to him in various ways. It’s very frustrating to my boyfriend because he gets overwhelmed by it because it’s happening constantly. We’ve been dealing with this for almost a year now. He is also more needy than normal and smothering to the point that my boyfriend is agitated by hIm . He doesn’t like to play by his self and sometimes my boyfriend wants to do things but he’s not able to because his son wants to be up under him all the time how can we get him to be a little bit more independent?