we throw around "Robby sees himself in X character" too liberally sometimes, and I say this, because often, it's easy to forget that while there may be reason to speculate— it's not necessarily canon. it's parallels that we draw, it's headcanons, it's things we see as the audience that the characters don't see for themselves, etc.
the only person that robby canonically sees himself in is samira. (and BJD— who he's basically using to project onto, lol. abandoned baby and whatnot. him comforting her was very clearly a way for him to self-soothe.) it's reinforced by parallels, similar character traits, and their tense relationship.
now, I've seen good posts on how all of the pittlings share so and so traits with robby, and they're fun to think about and interesting, but this doesn't necessarily mean he sees himself in them. most people don't really think like that in general. there are coworkers I have that share a lot of traits with me, technically, but I don't see myself in them. it's not a reflection, it's similar ground. if that makes sense.
dennis is the biggest character I think it's insisted upon that robby sees himself in— and I argue against this. I've never agreed with this perspective, tbh. him and dennis can be pretty different. robby sees someone who likes him, listens to him, and respects him, in dennis. not a mirror of him. if he does see anything reflected, it's the teachings that dennis regurgitates, which is not a mirror to robby— it's, again, a sign of respect. that maybe robby hasn't failed everyone. the core dynamic between them is the fact that dennis saw robby at his most vulnerable, in peds, and still likes him and respects him.
santos is another, and while I agree, they share that same ER cowboy stuff, that same dry sense of humor, etc... they also differ in a lot of ways. I think the common ground makes robby take a liking to her, but I don't think he necessarily sees himself in her. I think it's just often thrown around "he sees himself in victoria's intelligence!" "he sees himself in trinity's humor!" etc etc... maybe he likes victoria for her intelligence, or trinity for her humor, and he himself is also humorous at times and intelligent at times, but that's not a narrative mirror.
that's the entire reason why him and samira's dynamic stood out. because she is more of a direct reflection of him— sure, he can handle people who have similar traits here and there. but samira is a true mirror, and not just to his good parts, but also to his flaws. this causes the clash. (yes, some of it is his biases, but this is the root cause. the two can coexist.) robby is a man who hates himself. if he sees himself in someone, that fully, it doesn't, hasn't, won't go well.
samira is the only canonical mirror to robby. drawing parallels is fun, finding similar traits is fun, but it's all just headcanons, at the end of the day. (and also sometimes it takes away from the full characters tbh. dennis is not robby, dennis is dennis. trinity is not robby, trinity is trinity. yk.)