What I have found in "family" tents is take the number they say that can sleep in them and knock 2/3 off the top and you will get close to the comfortable limit.
I have the Cabelas West Wind Deluxe 8 man tent (12'2" x 14'). It is a great tent. Once you get all the gear and cots inside for a weeks hunt, two people is about perfect. Three is OK. Four is cramped, and if inclement wheather keeps all of four inside for an extended period, someone would be "Donner food" before to long.