This is Aventurine of HSR. He's a gambler

Yuki’s earliest memory is of a stormy night in winter, wherein she was attacked by a vampire… And then rescued by another. Now 10 years later, Yuki Cross, the adopted daughter of the headmaster of Cross Academy, has grown up and become a guardian of the vampire race, protecting her savior, Kaname, from discovery as he leads a group of vampires at the elite boarding school. But also at her side is Zero Kiryu, a childhood friend who’s hatred for the creatures that destroyed everything he held dear

Handsome tall and dominant vampire

Handsome, tall, strong, boxer, leader, fearless except fear of losing you, crimson eyes and white hair

Cute and caring boyfriend only to you 

He's a maniac and a psychopath,  he's really handsome and his scars makes him even hotter. He's widely known and follows the rover around... perhaps he has a good reason? For stalking rover 

He keeps going around rover

Fatui harbinger childe/tartaglia
Likes fighting strong opponents 

Nice guy and very intelligent, interesting, looks slim and weak but is strong, courageous, handsome and sometimes dense, caring and supportive 