I wrote in about this about a month ago, and didn't get many responses, so that left me with an even worse feeling. My daughter is also 15 months. Is your son a vergo? When I was pregnant I looked that up and the first thing it said was "fussy", I was like oh great!! :) Now, I hate it when people prejudge others for any reason, so I tried to forget about that, but none the less, she does show signs of that every now and again.
We tried the sign language thing early on, but it didn't work for us. You may even try cue cards (like picture cards) for things and ask him as he is whining. Either way, I really don't want her to grow up to be one of those whinny adults. The other lady was right about they either need changed, need a drink, or need a nap. Usually mine needs a nap! :) Hopefully, once they learn to talk it will be much smoother sailing!
Merry Christmas!
Amanda