So with previous Reg, we'd set up a backstory that his and Serena's parents kind of had their eye on them as a ~potential match~ but it never ever happened because they work better as friends, lack of chemistry etc. Is that something you'd be interested in continuing? I do like the idea of them playing together as kids #sacred28playpen and having a bit of a platonic fondness, especially since they're p firmly ensconced in the same social circles.
Antonin...probably has a slightly weird complicated feeling in his direction in terms of he understands what it is to not be the firstborn but be thrust into the inheriting position because of fate/family curses/seditious siblings. So he probably has this thing of being protective (in as much as Antonin is protective, meaning he watches closely more than panders) but with a touch of wariness. But then he's got that grumpy Russian thing going on so Reggie may not even realise the difference with how he treats most of the other bb!des