It depends on the color, do you have any photos of the existing leather sofas?

The chair is a tobacco I guess they call it. I haven't bought the sofa yet but we have this great leather chair that we love but are having a hard time figuring out where to put it in our new house. We want to go with a leather sectional in our living room and thought that the chair, the sectional and then a fabric chair would look nice. Not sure though. I'll try and post a picture of it and you all can tell me what you think.

the chair also has an ottoman btw

I generally tell my clients not to do so... especially because the room is going to end up with a cold sort of feel to it. You need to incorporate some fabric.

I would recommend a slipcovered sectional sofa, maybe potterybarn or something similar and I would pic a lighter color to contrast with the dark chair. Then you can add fun colored pillows which can be changed out seasonally if you would like and your last chair can be a patterned fabric chair.

Maybe tobacco is the wrong color I am saying then because it is not dark. We have small children one with allergys so we like darker leather. its cleaner and stains come out easier.

I have small children as well and that is why I suggested slip covered pieces. You can take them off and throw them in the wash

Great question! The best way to make this work is to accessorize with throw pillows, rugs, and drapery, and other small items that integrate the fabrics of both pieces of furniture. For example, have some leather on your throw pillows, as well as fabric.

Also, having many different textures in your room (a shaggy rug, textured pillows) can make your mismatched furnishings look intentional. Another way to draw the eye away from the mismatched pieces is to create a focal point. A great way to do this is with a beautiful mirror or painting, or pendant lighting of some sort. Overall, matchy-matchy living room sets are on their way out- people are preferential to variety nowadays. See some ideas below, and good luck!