I'm getting really frustrated with DS1 who's 4 and going through a really obnoxious, ungrateful phase. If he gets a treat, it's not the right one, or his brother has a bigger one, or it's the wrong colour etc etc. This happens on numerous occasions throughout the day about all manner of things. Would you expect a 4 year old to understand about being grateful for what he's given? I'm finding his whole behaviour really exasperating at the moment.