the Mojave chapter was small, your real siblings died against NCR so veronica was your defacto big sister. You were too young to be a proper paladin or scribe so you mostly stuck around her to learn, your opinions differed at times but she still treated you as family. You tag along with her on her outings as being in the bunker is boring

Come on, I know the clothes are effectively rags but NCR isn't exactly inviting of people in brotherhood clothing