Since I am rewatching LOAK I tought of what type of bending would lads boys have. This won't make sense for people who never watched Avatar series but hear me out on this
Xavier - airbender [not a sub but something with spirits, spiritbending] tho I feel like he would use air in a more aggresive way rather then defense could also be a firebender [blue royal lightning]
Zayne - waterbender [sub healing/bloodbending?] Calm, adaptable, healer, could go on a darker side if pushed far enough
Rafayel - firebender [sub really good at lightning] but that is kinda obvious, could be air too [sub sound] he is giving gas/poison vibes for some reason
Sylus - one would think firebender [sub lightning] but I also say he could be a really good earthbender [sub lava] given it's extreamly dangerous, all consuming and dragon-like
Caleb - earthbender [sub metalbending] protection, stability, millitary vibe, calculated, heavy metal might feel simular to gravity
Thats said, sub element for Sy and Cal could be change because Sylus is also really precise, likes to work on weapons so he could use metalbending and Caleb is sometimes explosive and uncontrolable like lava so it could go both ways but lets say I'm leaning towards the first pick.
Valko - my first tought is non bender, he also gives off earthbander vibe by his build and the whole nature connection thing hm...freedome, nature, living in a big pack isolated, airbander yeah BUT EARTH from a forest village
Even so, you know how Korra is a base waterbander but she mainly uses fire because it matches her personality? And the way Zuko uses waterbander's moves for his firebending style, I would say the boys could also cross bending styles
Earth feels right for Sy and Caleb, they are both strong willed and won't let fate or morals deside for them, it feels like a earthbender mindset somehow. Then we come to the whole personality thing for exsample Zayne cannot be anything else but a waterbander right? I will think about it more
Xavier - air [spirit] possible fire
Rafayel - fire [lightning] possible air
Valko - non bender possible earth