ON THE TOPIC OF XS AND HAIR.
Hair, is important to them, the more obvious and known of the two is Squalo’s hair. His hair being important is common knowledge in the fandom, no matter if you ship them or not.
It is revealed in the story with a panel (or scene) of him making a vow to grow it out until their plan of taking over Vongola is realised.
Squalo continued to grow his hair out for 8 years waiting for Xanxus, knowing the plan would never be realised no matter what they did. Xanxus is unable to rule Vongola because he is illegitimate but still, he waits and fights for him.
He continues to have it long in the Tyl arc, after Xanxus seemingly accepts that he is the Varia boss. We see that Xanxus chooses to strengthen the family in any way he can even if he's in the sidelines (declining Rasiel’s offer), valuing strength over blood ties… instead, Squalo’s hair, like his cut off hand, become a symbol of his devotion to Xanxus rather than a thing that needs to be cut off once their goal is achieved. The difference between a hand that is essential, dominant, and unable to grow back, and hair that only grows, needing to be cut due to impracticality- to be proof of his loyalty is notable to me.
Not only all of that, but, the way Squalo has his hair and treats it also shows how he feels about his vow to Xanxus or Xanxus in general. He has it untied and free- impractical for a man who weilds the sword and fights in close quarters. It proves his strength as a swordsman, bring able to fight and still keep his hair intact, and show it off- despite no one else knowing of the vow.
In the games, Squalo is really protective of his hair. When Dino trips and falls, he moves quickly away and is irritated that Dino had nearly touched his hair. He does let Lussuria touch it, but only because they offer to put nice hair oil on his hair for him. But he lets Xanxus throw things at it, pulls at it, and stains it with things that take three days to wash out.
Blah blah blah, we all know this. Not what I was supposed to be yapping about (shocker). What's more fascinating to me is that after making that vow- he urges Xanxus to do the same.
Who bids Xanxus to do anything? Those words weren't a request, it was more of a demand. And Xanxus doesn't get angry or reject it. Him responding with “heh, worthless” could be interpreted as a rejection, but he follows it up with “will it do that hand you lost in the affair with the emperor any good?”.
Rather than opposing the idea, he pivots- as if in concern or to say that growing out their hair is not going to bring the hand that he lost back (I am surprised he didn't even insinuate Squalo is unfit to follow him because of it) to win Xanxus the title of Varia boss.
The main thing is- Xanxus doesn't deny Squalo. And in my conclusions, he even goes along with it in his own way.
After this, Xanxus suddenly has accessories in his hair. We don't see it in the other flashbacks set before the conversation presumably took place (Xanxus beating up other mafia members, him reading about his illegitimacy, Squalo seeing Xanxus for the first time) but we do see it durring his fight with Nono before he got frozen.
All of this is assumption and speculation (as many things with Xanxus are), but it could be a way to highlight how his hair is now also a symbol of his goal for the Vongola- like Squalo’s hair is. Instead of just growing it out, he adorns it with red feathers, string (the stings are blue…… what else is blue…… not any other colours Xancus?? sus….) and raccoon tails almost to affirm his desire and intimidate anyone who gets in his way.
Xanxus does get frozen so seeing if he would actually grow out his hair is impossible.
But! In tyl, while his hair isn't long, though he did grow it out, he has a section of it at the back of his hair (a rat tail lmao) that is longer, wrapped tightly in a red ribbon with a single blue string attached to it. The abundance of accessories he wore when he was younger decreased, with only a few feathers in addition to the ribbon and string, and no raccoon tail. He doesn't need to scare anyone off anymore because his priorities are now different. Nontheless, Xanxus is reciprocating the vow that Squalo had made. Not as overtly as Squalo is, and like most things- hidden, doing it in his own roundabout way.