The first one has a few anatomy issues... the major thing I notice is that her shoulder is way too low. Her bum also has an unusual shape. x3 I tried to find a couple poses similar to hers to see for reference:
In your picture, from the top it looks like she's kind of hunched over. But her abdominal area and legs give the appearance that she's sitting with straight posture. Also, I can't really see how her neck connects to her shoulders.
The second picture looks quite interesting so far. :3 And I don't have any crits for that so far. <3
The third... I dunno, something about his mouth really bugs me. It looks like a fish mouth or something. >__>
This reference pic might help you out. You can see how the side of the mouth curves to the shape of the cheek, while turned at that angle. You can also see that the other side of the mouth (the right side on the reference) makes a more circular shape.
The nose looks like it could jut out a bit further, and have a more noticeable bridge. The chin bugs me a bit too but... I'd really have to see the reference picture you used to give you any further advice. XD
Nice stuff!
