Yes, Seki is the one-horn who accompanied Diamant out of their mountainous dark homes. They have not seen each other since, being only companions on the journey outworld. It would be appreciated to have familiar company, but Seki was an odd type, for their naturally high status, so maybe it is for the best that they parted ways and learned about the new world about them.
They have gotten into many a scuffle, which is a bit embarrassing considering Sho is so tiny-- he sure packs a punch though... They don't agree on much, and yet find each other stuck together far too often.
Oh, Cyg's inflated ego takes so many punches from Glasses, but there's always things that build him back up in NO time! This Dainty loves that he has someone to drive up the walls. They mesh well together, but it manages to be in unexpected ways (certainly not because Glasses can be the voice of reason or moderation). ...And of course all are welcome to thank Cygn for his near-aggravating domination of 'blessing' Glasses with his nickname... He's quite proud of its effect on the older man.
Cyg is annoying, but he's really hot. It seems like Glasses loves to yell at him and lecture him more than anything. But he lets Cyg stay with him all the time (maybe because he's lonlier than he lets on). Cyg really is quite fun and exciting even if they are both kinda jerks. That's why they work.