Adelie: Meant her during Quidditch after he saved her from a calculated and deliberate act from another slytherin to knock her off her broom with a bludger. Zef respects Adelie not only for the fact that she often worries about him, but also because she is gentle and kind even if he does find her too trusting of others. They both get a long well even though she often gets embarrassed when Zef is blunt. She introduced Zef to everyone else in the group.

Rin: Rin and Zef are what you call rivals in a lot of ways her being adept in DADA very much like he is they are always having little duels here and there to try and overcome the other which usually ends in a draw. Zef respects Rin for her ability to drive him to the edge when dueling and her attitude that has no end. They are probably among the closest in the group if not because of their friendly competitions but it depends on whos looking at it. Meant Rin through Adelie

Stella: Stella and Zef have what you might call a tin and foil type relationship, while they both have respect for each others morals they differ widely most often being that both have tendencies to do things the other disagrees with. But in reality this is sort of the same thing that makes them friends, you know what they say opposites always tend to attract and work in the end. Meant Stella through Adelie.

Calvin: Respects Calvin deeply not only because of their pasts being eerily similar in some ways, but because they both have nightmares in their pasts and they both strive for something more then that past. Also being the only males of their group they more often then not have banded together and Calvin is the only one he has ever really shared the truth of his past with. Meant Calvin through Adelie as well.

Ok I did my best on this haha my head has been so bloody all over the place its hard to write xD