My16month old doesn't talk, is this ok?

I am a first time mother and my 16month old doesn't talk. He says "mama" and "dada" and occasionally "no" but other than that, he shows no interest in talking. He does, however, understand a lot. He knows where his eyes, nose, ears and mouth is. When I ask him to get the ball or remote, an he will. He knows when I tell him to open or close something. And when I ask himto clean his toys, he does. He just doesn't want to talk other than normal baby babble. I have a nephew a month younger than him and he talks a lot. He can say names, apple, bye bye, dog, sister, "I love you". So it just concerns me a little. I wasn't so worried until my family pointed out the fact that he doesn't watch t.v AT ALL and he doesn't really socialize with other kids much. I know every kid develops differently. He developed everything else very early. He rolled over at 1-2 moths, sat up at 4 months, crawled at 5 months, started standing 7-8 months, and started walking at 10months. I believe that he's really smart, I'm just a little concerned now because my family put ideas into my head.