Since your living/family room is a walkthrough all the way around, it leaves you with about a 13'x13-15' area for furniture placement. It really depends on how you would want to furnish the room. If you were planning to do a U-shape facing the fire place with sofa, loveseat, and chairs, you may want about 8 more inches to really give enough space to move around. If you were looking at a sectional that has equivalent seating, you have likely have plenty of space.