“Sam! Sam!” Celia’s voice was grating and nasal.

I’m pretty sure we don’t know a Celia – or at least don’t know that we know one – but do we know a Sam? I’m not really sure. I don’t think so, but it’s a common enough name that it ends up sounding familiar nonetheless.
I’m going to guess he’s a hero, though. Sam is a very heroic name.
Meanwhile Celia so far sounds like a somewhat annoying (to Sam) little girl. It would be entirely possible for this to be Bonesaw and another member of the Nine, but they seem to stick to their cape names (in the cases where there’s a difference) when talking to and about each other from what we’ve seen, with the exception of Jack reminding Mannequin about his old self. Besides, I feel like we’d have a description of Bonesaw’s voice earlier if this were her.
“I’m coming!” The heavyset man grumbled, as he made his way into the living room. Celia sat on the floor between the couch and the coffee table. The white of her t-shirt and panties was a stark contrast to her dark skin.
Definitely sounds like a kid, yeah.
Sam leered at the woman. She was good-looking for her age, slim, though her breasts sagged behind her shirt without the benefit of a bra.
…but apparently she’s not. Fair enough, I was basing that on almost nothing anyway.