Currently, Rosaline Weyenburg (20) is the only one of their family who is old enough and involved enough with the public to meet and possibly befriend a hunter. I'm also definitely up to any romantic involvement as that would stir the pot and bring up plot things, as she is also unmarried/unengaged. The two younger Weyenburgs are also available to meet with the hunters at some point and befriend them, though they are too young for any romantic activity, plus Emmaline is engaged to the King's son and Charillos is 7.
As for the Ballangers, Lancelin (24) is very stoic and somewhat emotionless. He is engaged to the King's daughter and takes his duty very seriously. His brother, on the other hand, Villiame (19) is a poet and lover of women. He currently fancies Anastasia, but, as Excal has left and Anastasia is almost twice his age, he would definitely be open to changing fascinations to another young woman if given the chance. He is also a bit too trusting and could easily slip some noble secrets to a lover. Eudeline Ballanger (16) is off the table romance-wise because she is very dutiful and is engaged to Luther Filtiarn. She could always befriend someone, though.
As for the Filtiarns, you would have to ask
@LordLinguinie as he is mostly in control of them. Luther and Elaine are both spoken for, but Luther is a known womanizer. Elaine also is not in love with her husband, the King's brother.