Anais - hmm. Well, what's left of his family lives in Canada? I think I put down that the farm is in Ontario, but maybe a sister or two lives out in the maritmes? But he likely has about as much to do with royalty as... a very unlikely thing. He's pretty keen on quidditch though?
Osgar - They were only a year apart at Hogwarts? In not totally unfriendly houses? So they might at least be aware of each other from that? (Mixblood bastard with chip on shoulder, exceeds expectations, aims high, achieves nothing.) Also he was sponsored by an as of yet undetermined full blood family, so he went to all the requisite social events, etc as a not entirely respectable participant. The charity kid at the children's xmas party, slowly dying inside. They may have run into each other to some degree?
Joseph - Ditto the whole being sponsored thing. Could have run into each other there, though Michael was on his way out of the system as Joseph was on his way in? Or maybe somewhere in the ministry? Michael is just the one in the background behind the secretary for magical law enforcement, being efficient and taking care of things.
Cassandra - Since she's an Irish pureblood they're probably distantly related seeing how his grandad was a Yaxley? But the chances of them knowing each other or interacting seem pretty slim what with her being at court and him in Diagon Alley.