I mean honestly I had two females in a 20 from when they were babies, they're about a year and a half now and I only just recently put them in separate 20's. They never fought and always slept together, hunted crickets together, etc. They just weren't getting much bigger, so if anything you can potentially keep them together if they're little but definitely separate when they get older/larger. It could stunt their growth if they continue to be in a small space like that.