Junior was the previous business overseer of the club. Although the club was destroyed by Yang Xiao Long in the "Yellow" Trailer, it was shown in "Painting the Town..." that the club had since been repaired. Following the Fall of Beacon, Junior was likely forced to abandon his club due to Grimm entering the city.
Miltia was a member of Junior's Club and was one of his bodyguards due to always being at his side.
Melanie was a member of Junior's Club and one of his bodyguards due to always being at his side.
Not much was known about Roman's relationship with Junior, except that they were business partners in some way. This was demonstrated by Roman's brief appearance in the "Yellow" Trailer, discussing an unknown subject with Junior. Later on in "Ruby Rose", some of Junior's henchmen were seen under Roman's command in order to assist him in robbing the Dust shop From Dust Till Dawn.
After they were defeated, Roman claimed that they were "worth every cent", suggesting he hired them from Junior. This was later confirmed by Junior himself when Yang questioned him. They have since ceased contact with one another, likely due to Roman's disappointment with Junior's men's performance.
Yang's acquaintance with Junior is short but eventful. Yang originally approaches him for information regarding her mother Raven Branwen, even hurting Junior slightly in the process to get an honest answer. Even after this, when Yang offers to kiss and make up, he is not above accepting her offer. When he is knocked out, he has small hearts circling his head, implying he is at least somewhat attracted to her.
Later, Yang is responsible for damages to Junior's dance club and the assault on Junior and his associates. When Yang later returns to question Junior about his ties to Roman he is shown to be visibly nervous and intimidated by her presence, likely owing to their previous encounter.
In Chapter 9 of the manga, after his fight with Yang, he appears to be friendlier toward Yang and meets her sister, Ruby Rose. He was also willing to help her by giving her any information he had regarding Raven. However, he later revealed that he really didn't know anything about Raven and was unable to help Yang with her search for her mother.
Junior only crossed paths with Neptune once, when Yang brought him with her the night she returned to his club. He ignored Neptune initially, then seemed largely unimpressed with him, calling his question stupid and asking Yang who he was.