I don't understand this young generation and home sickness. Home sickness isn't uncommon, but usually it goes away after 6 or so months once you settle, he has been here long enough to have gotten over it by now.
I don't think it is the kids fault, just a fact that modern young generations are coddled well into their teens and adulthood that they simply cannot cope without their parents. It doesn't prepare them for life, all it does is reinforces their dependency.