I've been referencing Thom and Aldous as friendly ever since we decided they were on good enough terms to merit Quidditch box invites like two years ago. Both UCPBs, similar politics for the most part (Thom is progressiveish on things but he's a traditionalist at heart, he just likes to think of himself as progressive). They were also roommates in Slytherin if I did my math right. If I did my math wrong it's only off by a year, so. Thom could also commiserate with Aldous' younger brother troubles since he hates Art so passionately and feels personally affronted by his lack of usefulness, so they've that in common. xD

Technically Magnus Lockhart fits your criteria for Atticus but given that 1) Lock doesn't really talk to people, generally speaking and 2) he once nearly burned down the Irvingly Arms in that one thread, I don't think it could be a pre-established thing. I'm up for threadding them in the future to see whether they could become friends if you like but for right now not much for you.

Ernest Mulciber is not progressive but is apolitical enough not to mind that Balt is, if they were friends from the DoM? Would 100% have cut ties after the Topaz thing, though.

And I will have a new girl for Roslyn in the future — Esther Browne (aged 27) is her sister-in-law through Ross' brother's wife so roundabout family. Es is Not Wonderful in big social events and much more comfortable befriending family or friends of family in small groups. I think their interests are similar, in that Esther is interested in supporting her husband, staying largely out of the limelight, and gardening. She'll be around sometime later this month or early next.