Studio lighting help

I am still learning how to control my studio lighting and need some help. I have an AlienBees 400 and 800 and a large octabox and medium softbox.

My goal is to get even lighting on a group of 3 and any shadows to be light and soft.

This is in my home with a semi large room, with a large window in front of my backdrop about 14' between the window and backdrop.

Lately our ambient lighting has been rather dark, a lot of dark heavy overcast days..what is the best way to position my 2 lights? Is it possible to only use 2 lights to get a nice bright, soft shadow look on the subjects and help light the background as well or would I definitely need to get a 3rd?

I did watch the inverse square law by Mark Wallace on youtube and it states the farther back the light is, the less light fall off so I tried backing my lights up as far as my room would let me when taking a halloween picture of my 3 girls, both lights at a 45 degree angle, one on each side, but I didn't get nice even lighting on their whole body and still some harsh shadows.

I also read the closer the light the softer the shadows, so how do I get all 3 people with soft shadows and even lighting so there is little to no light fall off?

In a studio environment most of the time you don't want any ambient light in your exposure, especially if you're learning the basics. I'd also just work with one light until you feel you have a solid grasp on how to use it. Don't worry too much about understanding the inverse square law - just remembering "the farther the light from the subject the less power" is good enough and allows you to focus on important things like understanding quality and direction of light. I would suggest investing a light meter and practicing the classic lighting techniques that can look fantastic with one light: rembrandt, paramount, broad, and short. Learn how different modifiers work (umbrella, softbox, reflector) and their associated techniques like feathering. Good luck!

Sounds like you have a basic understanding and just need some practical application. I assume you're shooting digital, so why not get some people and experiment? You already understand that the larger the light source, the softer the shadows. Your lightboxes and such are a good start, but what else do you have? You have a huge window which on an overcast day is nothing but a giant, flat, softbox. Reflectors can be used to kill shadows as well. Ceilings and walls, if white, can be turned into huge light sources as well. Usually you think of bounce flash with an on-camera speedlight but there is no reason you can't bounce your bees even with the softbox on. That's what you use an umbrella for.
If you got really creative, you could create a wall on wheels that is flat white that you can use as a giant positional reflector.
I'm only scratching the surface. Many things will work and many will have similar results. It's hard to say without being there but that's where experience comes in. So get in there and goof off a bit. It's digital, so it's free.

Keep in mind the characteristic of softboxes, that their intensity near the edges drops off. You can use that characteristic to your advantage!

This illustration shows one light. Aim the softbox so that the edges of its field fall on the closest person, while the center of the softbox falls on folks farther away, where intensity also falls off due to the Inverse Linear 'law' of large light sources. Do the same on the other side, and you can achieve fairly uniform lighting across a larger group. Best to try this for the first time with a large uniformly colored wall, and also have an incident meter to further quantify the eveness of illumination field.

There are two main qualities to keep in mind when it comes to shadows. Hard vs. soft shadows is usually in reference to the shadow edges. Soft shadows have a soft edge that creates a smooth transition from highlight to shadow (such as created by a large softbox or window). Hard shadows have hard edges that create a very quick transition.....hard and soft shadow generally applies to only how the shadow edge transitions. The second is shadow contrast, which is how dark the shadows are as compared to the highlights. You can have soft light while still having very deep dark contrasty shadows and you can have hard light while having very light low contrast shadow areas and vice-a-versa.
With two lights, a good place to start would be to place one light with a large softbox near the camera axis....just above and behind the camera generally works nicely. This is going to be your fill light and should give you a nice even, soft, flat light with very little in the way of shadows since it is as near to the camera axis as you can get. Once you have that light positioned, you can add your key or main light....the purpose of this light is to create dimension by adding highlight and shadow areas to your subjects. For a group of people, you will probably want to position it just to the left or right of the camera and a bit higher than your fill light......a 45 degree angle would probably be a little too much for a group (play with the position to get as much or as little shadow area as you would like). You also have to be careful with groups to make sure that the shadow from one person isn't going to fall across someone else in the group.
From here, you need to balance the lighting between your fill and key light (a light meter is really handy to have for this part). Meter each light separately, making your key light output is slightly more than your fill (1 stop difference is a nice place to start). For instance, if your fill meters at f5.6, meter your key for f8. If the shadows are still too contrasty for your taste, dial back your key a bit. If you want more contrast add more power to your key light (just remember to adjust camera settings for any changes you make). If you're shooting with a large window behind you, you could potentially use that as your fill light (it should act as a large softbox positioned just right if it's right behind the camera). Just meter the light from the window and adjust your key light in relation to the natural light...just keep in mind that this may cause some WB issues if the strobe light temp differs much from the natural light temp.
Another option that's even easier for groups is to use a single large softbox just behind and above the camera (basically just your fill light set-up only I prefer it to be slightly higher than a fill light). This requires very little in the way of adjustments and it usually prevents issues of shadows from one person falling across someone else.

For additional clarification, what jra describes is useful for a somewhat smaller group of people or individual, where the Fill near camera position can cover the entire group. Then the Main light can provides facial detail and dimension, also across the entire group.

In comparison, in post 4 I describe how one can two two large softboxes to light a fairly large group . The coverage area from a single light source is insufficient to cast light on the entire group. So the feathering technique which I described takes advantage of the softbox characteristics to increase the effect are of coverage in a somewhat uniform manner (in terms of amount of light falling on person closest to light source vs. the one standing farthest away from same light source), and you can do that on each side of the group to cover a very wide front in a rather uniform field of illumination. Yes, there is less emphasis on facial modeling and more emphasis on simple illumination of the subject group.

We are not contracting each other, but we are describing two different techniques, one suitable for one size group and the other suitable for a larger size group.