As for Francesca and Davrin, they'd probably marry very soon after dav end. The Calling may not be a thing anymore, but as Wardens the sense of urgency is still there, so they'd probably want to do it as soon as possible. It'd be a dalish marriage, in Arlathan ;A;

will ABSOLUTELY want to be involved jdhdjfb
I mean, it's not for everyone to have the Divine as your marriage officer and the King and Queen of Ferelden as witnesses hdbdjdb

he's not against it, but he doesn't see it as something THAT important in a relationship. But with age, he'd probably grow to be less cynical and see how important is it for Lucanis ;v;
I don't know if it'd in Denerim or Rialto, but Alistair, Anora and Leliana...

But, Andrea is also quite young (21 yrs), so I think there's a chance they will end up marry in the future, especially once he's more mature and at ease with his feelings ;v;
He grew up with Alistair and Anora married but not in love and his parents being the direct opposite;

As for Andrea and Lucanis...I really don't know. Lucanis does struck me as a very romantic person and would probably want a proper marriage, but Andrea already panicked accepting he was in love, so he fears a proposal would probably make him flee again---

Then she stays mostly in Lavendel, but sometimes goes to see Andrea (or Davrin, as they have "something" going on from before) at the Lighthouse~

They meet again in the War Room during the siege and almost instantly recognise the other even though they did changed A LOT (Francesca did know about his brother transition though, he wrote her about that).

They are still overprotective on the other, especially Andrea, as he feels a little guilty for having been able to stay with their parents, even if the choice wasn't his to make.

Their relationship is...well, they do care a lot about the other and constantly write letters, but were also separated when they were 10, with Francesca forced to stay in Weisshaupt and Andrea with their parents roaming Thedas: so it's strangely good, I would say?

(...)
she has, although, a particular innate talent on shape-shifting, the only magical-thing she does (if we don't count the "power of blood" magic).

That's balanced by Zevran and his more physical approach to expression of love and care: he also sometimes worked as an "interpreter" for Venehn when she didn't know how to talk with their children and makes them upset ;v;

As for the actual parents, Venehn has always been a stoic, severe and strict mother, passing them all her knowledge (esp on blood magic), but been a bit distant and less prone to pda: she would reciprocate but very rarely initiate and hug or similar.
(5)

Leliana hasn't been present as much because of her role of the left hand and then divine, but she still spent a great time with them, especially playing dressing up. Once only Andrea remained and was older, she imparted him her knowledge as a bard and former spymaster.
(4)

Alistair especially has grown very close to Venehn's children, becoming a "broody hen" when any of the two is involved. His meeting with Lucanis was...well, interesting.
(3)

Especially the last two, as the twins spent a great amount of their childhood in Denerim, getting spoiled by Alistair or schooled by Anora; not to mention, been blonde, it wasn't rare for them to be thought to be Alistair's own children---
(2)