Epsilon no longer remembers a time before Suyis, and frankly, doesn't care to. It's most likely that her memory bank was wiped at some point, and Suyis wasn't able to restore it. It's not like it matters. Suyis says that the dating on her internal components suggests Epsilon is one of the first daeni to exist in Tyrrhenia, but he's not sure what that means and neither is she. He found her parts scattered around a junkyard and, always one to enjoy a challenge, gathered them all up, matched them together, and then started upgrading them to get her to run again.
It seems fitting, to her, because Epsilon's always felt like her life didn't really begin until she met Suyis. He gave her an updated chassis, upgraded her operating system and several internal components, and then outfitted her with state of the art weaponry. Packed in her tiny little body is quite the little arsenal of blaster weapons, and a few non-blaster weapons of lethal design. Epsilon is not the bodyguard daeni, that'd be Delta, but she operates in such capacity anyway.
It wasn't until recently that she started wondering why, and then realised that she placed more weight on Suyis' safety than her own. She can be put back together. Organic creatures can't always. It seemed like sound reasoning, and even Delta thought so, but the more she considered it, the more it seemed like it was an excuse of some kind.
More accidentally, she's continued to challenge the concept of humanity. She doesn't know what a relationship with one's family members might be like, exactly, but she imagines it to be something like the relationship she has with Suyis and Delta. Much like her, Delta was also discarded and unwanted; until Suyis came along. It wasn't like they were aware they weren't running, but it's still somehow nice to know someone wanted them, and Epsilon's under no illusions. Suyis is playing chicken with danger, and she knows it, and he knows it, and Delta knows it too. Someday, things will get rough, and when that day comes, Epsilon has every intention of fighting with everything she's got for Suyis' cause, because even objectively, it's a decent one.
For now, Delta manages Suyis Corps' security, and Epsilon manages the front desk. She's the one most interact with for escorts, to see about Suyis' scheduling, directions, and general inquiries. Epsilon can't say she's fond of the particularly rich clients, but overall her job's not a terrible one, and she's always aware of where Suyis is.