It should be a nice family, especially with the older kids helping with the younger ones and such (though it wouldn't be fun for some when they want privacy). It would be interesting to know how a family that large manages to operate, especially with all the activities that kids today take part in. But the whole extended family must be getting in on the raising of the kids if they are getting by, so good for them.
I knew a family with 5 boys --- all teenagers at the time who owned a quite small 2 bedroom house --- the parents had one room and all 5 boys slept in the one small bedroom --- wall to wall beds. So really you'd only need 3 bedrooms for 15 kids --- less when they're little.
I've seen big families --- a friend of mine was oldest of 11 and 9 of them were born in 10 years --- they'd line up the babies at diaper changing time --- 3 or 4 in a row --- if you're changing one diaper it's almost as easy to do 4, baths were given in the laundry tub -- 2 kids per side, 4 kids at a time. My uncle had 11 kids -- they had a big van to travel in and on camping trips several tents --- they weren't poor either, he had a pretty good job.