Second attempt at portraits

After my first mess about attempt which I got some advise on I have a few more attempts trying a few different styles. My favourite is shot 4 which is of my 2 girls and have had that printed at A2 size and framed but still think it could be better. I did not have room to get a hairlight( think thats what it is from behind to make them stand out from the background a bit more) and possibly need to bring my flash comensation down a bit as losing detail on the faces but any other C&C are gratefully accepted to see whichh way I should look to go and what improvements i need to make.

The hardest was the group of kids!!! whoever said never work with animals or children was right!!