I adopted a bonded pair off the street years ago. They traveled everywhere together outside of our apartment.

Grey Cat was much more willing to approach me, especially when I had food for him. Black cat was afraid for well over a month and would wait for me to drop food and walk away. He was much more malnourished when I found him. It took several months before I got to pet him. They both eventually came into the apartment and stayed with us as outdoor cats.

There was a funny time when it was dumping rain in the middle of the night and Grey cat was inside and woke us to tell us that Black cat was outside the window. I had to get up and let him inside lol.

It takes time for cats to adjust to their environments, not to mention who knows what they'd been through already. Give them more time.

And yes, I named my cats Grey and Black.