When your cat's crying, it means they want something. You need to figure out what that is.
Make sure each night you fill up their bowls, do their litter, and open most of the doors, except the ones leading outside, unless you want them outside at night.
My cat's usually only cry for food, water, or if they want in, or attention. The next time your cat cries at night, get out of bed and see where it is.
I hope this helped!! Good luck!!q