ok great then the the look but no touch set up will work great and at night use something like a dog crate to put the girls in, inside the coop with the boy. so they can still see but not touch yet. They need to get used to each other first., then supervise some together time and see how it goes.
they need the look but no touch set up for a week or more, where they can see each other through a fence. When they start to lay down near each other at the fence then you know they are ok.
Assuming they are 6 weeks old.
If they are only one week olds they should still be in a brooder with...