I just had a boy so I'm gonna comment on a few of these pics. I usually leave that to more experienced people but here goes:
1. Love the concept, and i think the selective color works well here (though many will say it is overdone) but your BiL doesn't really add to the picture, I think you need to work on a different pose for him, or maybe just get his hand and the marker.
2. I like this shot and the pose, but I think you would be better off going outside or against a plain wall. The background seems a little distracting. Also looks a little out of focus.
3. I really like this one! Again, I enjoy the selective color but many will say it's overdone. I think it would be even nicer if there was no clothing visible. I understand the whole sister thing, but just sayin'.
4. Nice pose, but I'm not sure him being shirtless really adds anything. Again I find the background a bit distracting
5. Love the belly+bow. I think you are on to something here, just find a nicer background. Also, less clothes would be nicer IMO.
Also, all these could benefit from some skin smoothing, blemish cloning, etc.