Milk's unseen kin, invoked in her own self-accusation that they would be ashamed of her.
Stung by Prepotente calling her a Former Crawler, Milk hears her own inner voice run through the indictment: you were a crawler, you fought, you were part of something once, and now all you do is sleep. You've missed entire seasons more times than you can count. You're a coward, that's what you are.
When was the last time you even tried to help someone? Your family would be ashamed. It is the only reference to her kin in the chapter, and the line that pushes her to say "Fuck it" and help the crawlers anyway.
The absent kin whose imagined judgment shames Milk into acting.