Sweet smile in the baby! Makes one smile to oneself in front of the screen, so infecting! And Big Sister is so pretty!
What flash did you use?
It looks sort of direct, yet there is none of the (very dreaded by me!) sharp shadow of on-camera flash to be seen. And still I feel it was quite direct and flattens the children's faces more than any flash set up at an angle would have done. Will you tell us?
The sofa makes the shot quite busy - what if you took a similar photo, in portrait (as opposed to landscape) and if you can't zoom in enough, use an aperture size of f5.6 or less so the background is faded/blurred?