Our 33 foot Travel Trailer is about 300 sq.ft. My wife and I and two dogs and two cats get along just fine for 3 months of the year when we travel. Our regular home is 2100 sq.ft. and it is fine too.
There are a lot of small families living in campers/travel trailers/motorhomes in western ND, who came here to work in in the oil patch or spin-off jobs in spite of a housing shortage. Not easy for a family with a couple of rambunctious kids, especially in winter, but they are doing what they need to do.