Breeding and egg laying puts alot of stress on females regardless...though a trio in a large cage can work well. But this does depend on individual dragons. Some don't like cage mates at all and will attack them aggressively. Others couldn't care less either way. It all depends on the individual dragons and the size of the cage.
However, I always feel its best to house separately. Less chance of a sudden burst of aggressive resulting in a serious injury. There are also all the other issues potentially caused by housing multiple dragons. Competition for basking space and food, difficulty in knowing who is pooping regularly, how much each dragon is eating, spread of disease and parasites etc.
For two adult dragons I recommend at least a 5'x2' cage..or 4'x3' for additional animals I would add another 2' or more square feet. It is best to house a male and two females, to prevent over breeding of a single female...though I still think separating males from females is best, to give not only the females a break but the male too.
Setup is more difficult too as you want to make sure there are many basking sites that reach the appropriate range of temperatures so your dragon's are not competing for prime basking area (ie that 'stacking' look which some people find 'cute' when it really is a sign the dragons do not have room to bask separately, and the more dominate dragon is getting all the heat/UVB instead of the other dragon (dragons don't let heat and UVB pass through their bodies, so the 'under dragon' is cold and miserable). Making sure there is plenty of food for everyone but having more than one food dish, spread out in the cage.
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PHLdyPayne