I'm not certain whether I am qualified to give critique but I will do my best.
I like the posing and expressions, they seem pretty natural which is always good, especially the use of their eyes and directing their gazes. Some areas for improvement might be the hands, they look a tad out of proportion (I'm terrible at hands as well so I can't really say ;^ but maybe you could find references, or take a picture of your own hand in that position.
You could also add more highlights and shadows to make the piece look more complex or balanced, though the muted tones look pretty good as well. (it isn't exactly the atmosphere for sparkly highlights is it?) Personally I like strong shadows where you can actually see the crease in the clothing etc. The background is nice though, sort of reminds me of the mafia da?
That is all I have to say, I hope you find it somewhat useful