I'm just going to mention potential relationships that jump out at me. For the most part I'm sure mostly everyone would get along with everyone though. ANYWHO...
Audo: Victor also travels from kingdom to kingdom, also doesn't really acknowledge his relationship, and also thinks pretty highly of himself. They would probably either really get along or TOTALLY hate each other.
Nadia (Victor's wife (and I use the word loosely)) would TOTALLY bang the hell out of Audo.
Tar: I LOVE the plans you have for him and his family - it will be SO comical. I have one of my king's sons, his wife, and their daughter (they ran off to avoid the civil war) living in the Runic kingdom and I have ZERO plans for where they live/who they know/etc. Their names are Sascha, Mariele, and Ottilie. SO they could totally live near each other or potentially know each other somehow.
Torbjorn: If we do go along with the plans with Tar then Torb would probably totally dislike my peeps simply because they are from the Arcane kingdom.
Walderik: I could see there being some post-war handshakes as you mentioned. My king (Christoph) despises his father and didn't want to go to war with the Runic kingdom in the first place.
Jovina: I could totally see her getting kidnapped in the Pents kingdom (Sass has made those people all sorts of fucked up) and that would be TOTALLY hilarious. If she ends up being a slave then my character Tse would probably get to know her.
Runa: Not too sure about this one - we might just have to see what happens when characters get thrown at one another..?