A.O.
my niece is 16 months and doesn't say a thing. I said something to my sister since I watch her all day. I told her that I wouldn't worry about it yet because she understands mostly what you are saying to her. I can tell her to go get a toy and she will go get it. I don't think you should worry, especially if he is understanding what is going on around him. My niece has 3 brothers ranging from 14 - 6 so I just assume that there is so much going on and everyone is right on top of what ever she needs that she doesn't need to say anything.
I have been working with her more, like going through her favorite dora book and saying the words while she is looking at me and I have noticed she is trying to say dora. I did the same thing with my son from the begining and he was saying astronaut by the time he was one. I think if you try something like that with something he loves and just keep repeating it he might want to say it.
Good luck.