It's more like at 9-12 weeks to seperation between boyes and girls, depending on size, small breeds mature faster. The youngest doe of mine getting pregnant was just 14 weeks, and mine are 10lbs rabbits.
Females together can work in the right setup, that's how I keep my 3-4 does and their doelings now. It can happen that 2 characters simply don't match, that's why I had two pairs before.
Does have quite some social tools to establish a hierachy, never had them escalate inside a group.
Intact males together, well, nope. I keep my bucklings together for up to 16-20 weeks, but I have to watch them closely, which needs some experience to read the signs. If they snap, it can end badly in seconds, with serious injuries or death. Their incentive to fight is not hierachy, but to drive opponents away - which doesn't work in a closed space.
Even neutered males are the most problematic pairing and needs luck, luck and experience, and a doe just being nearby can upset that peace.
If you keep rabbits together be absolutly sure about there sexes. Check weekly (in case the Sex Change Fairy paid a visit, a frequent occurance...), and if possible get a second opinion. A buck accidentially ending up in a cage with the does is a very happy buck.