Quail will breed with whatever birds of their species are available. That said, genetically speaking, if you must breed them with close relations, it's far better to breed fathers to daughters / mothers to sons than to breed siblings. Space requirements vary by quail type and there are many types of quail. Knowing what type you intend to raise and breed will help someone address the issue on space requirements for optimal health and welfare of your flock. Some species prefer monogamy, others prefer a harem. Japanese coturnix quail, the type that I raise, require 9-square inches to 1-square foot of USABLE floor space per bird, and one cock needs at minimum three hens, up to eight hens if fertility isn't an issue. I house my birds in several 2x3' hamster-type cages (the kind with the bottom 6" of the cage is like a solid plastic tote, the top of the cage is wire). My breed of quail don't care to use ramps or fly to other levels. They prefer to hop up or down levels, I make each level only about a six inch hop and only wide enough for what's on the shelf (food & water, or sand box), with very little stand-around-and-make-a-mess room. By adding these levels, I'm able to open up some floor space for them by putting food and water on one level, and a sandbox on another while giving them full romping room on the lowest level. This is what works for me, what works for you and your flock may be different