KmH's post above has several basic, accurate statements. Every statement he makes is factually correct. I'll just add a couple items for thought. First, if you want to mimic window lighting, a square or rectangular-shaped softbox or light panel will give the same shape of catchlights. If you wish to mimic the old-time "north light studio" window look, then one of the easier ways to do that is to create a very LARGE light source, and one that is NOT so doggone close to the subjects...that helps in two ways. First, a really large light source, like an entire wall lighted by 3 or 4 diffused lights, creates a very soft (with soft-edged shadows) qualirty of light that has a lot of wrap-around effect, and is also fairly constant in its output across the shooting area.
There is a scientific fact or principle in the way light behaves, and it's called the Inverse Square Law. The practical aspect is this: when a light is pulled in really,really close to a subject, "like just outside the image frame", the large size of the light in relation to the subject does create a fairly soft lighting effect; BUT, and this is a huge BUT, that light drops off in intensity with AMAZING rapidity. From one side of a horizontal frame to the other, there will be a massive drop-off in light intensity, meaning the shadowed side of people will be quite dark. So, if you are trying to create a studio environment where you have this wonderful, natural lighitng quality, where you can pose a group of kids and just shoot away, then you are going to need to light the ENTIRE shooting area pretty evenly, and the easiest way to do that is to create a very LARGE panel covered with translucent white fabric and to shine 3 to 4 lights through that, or to create a huge "wall of light" by literally, creating a wall-sized light source.