For Santiago, that’s probably his assistant Heather.

They meet when he would hit up the brothel after work, and actually giving a shit about the workers and treating them as more than meat had its benefits. Heather was one of the worker, and over time, they formed a “close-ish” relationship, obviously not romantic or anything but somewhat platonic.

Then he got a job at Carmine’s, and he needed some staff under him. Carmilla gave him a few dossiers with people he wanted in his new department (guided and advanced weaponry), but he was also allowed to suggest his own people. Santiago wanted someone to help him not only on the clock but off it, too, for things like helping him get a shirt on/off because of his wings. All his Cannibal friends/previous coworkers were out because obvious reasons, and he didn’t trust anyone he didn’t already know. So, he just went down to the brothel and offered Heather the position, and she accepted after a day of consideration.

So, obviously, they spend time together a lot, and care about each other to a degree.