Gin has developed many relationships before and during the series. Some have been positive while others are negative.
Gin had a close bond with his mother and loved her dearly. She was the one who gave him his name and also was the one who gave him the surename "Yoarashi" Her death was one of the factors that pushed him to desire vengeance towards the Devils as well as master the art of Senjutsu and Yojutsu. The bond he shared with her made Gin decide that if he ever got married and had a daughter he would name her Akira. He also wanted to find and bring any survivng Nekoshous to Kyoto to honor his mother's memory.
Just like with his mother, Gin and his father had a close bond with one another. Christopher taught Gin everything he knew about Alchemy as well as gave him the lessons about the dangers of it and how it should not be used to create living beings. Christopher's love for his son was so great that he gladly sacrifice his life to save Gin's as well as implant the only Philosopher's Stone into his son when Gin was grievously injured, despite how long it took him to make it. His father's death was also a major factor for Gin's quest for revenge as well as push him foward to complete Christopher's work of creating the Philosopher's Stone without human sacrifice.
Originally Yoarashi did not give Koneko much attention, though it was more than he gave the rest of the Occult Research Club as he was curious why a Nekoshou would want to become a reincarnated Devil. They got to know each other when she was selected to stay at his place in the town per the contract Yoarashi made with Sirzechs. After the battle with Kokabiel the two recognized their feelings for one another and mated. That also made Koneko the mother of the orphaned Nekoshous under his care.
Yoarashi has shown to be very loyal and caring towards Koneko, helping her overcome her fear of her own heritage. She is also one of the few people who can get Yoarashi to show his emotions. His love for her extended that he nearly killed Cao Cao in rage when he redirected Vali's attack back at Koneko. Likewise Koneko also cares for Yoarashi and can become very jealous and territorial whenever a girl tries to make a move on him. He along with Kuroka, also began instructing Koneko in using Senjutsu.
The relationship between Yoarashi and Kuroka is complicated. Originally Kuroka was curious about him when she learned there was a male Nekoshou. Upon watching him in action and sensing the amount of ki he gave off, Kuroka tried to seduce him. Of course that put her at odds with her sister, Koneko, whom Yoarashi was mated with. After their first meeting she would continue to flirt with Yoarashi (much too Koneko's chagrin) but would sometimes be disappointed when she rarely got a reaction. After the battle with Cao Cao, Kuroka finally acknowleged that both Yoarashi and Koneko were deeply in love and stopped trying to seduce him. She now accepts him as her brother-in-law and is glad her sister has someone like him around. She always warns Yoarashi to treat Koneko nicely and wants lots of nieces and nephews.
Yoarashi's view towards Kuroka is more complicated. While he knows that it was her actions that caused the near extinction, Yoarashi also acknowledges that Kuroka did what she had to in order to protect her little sister. Their first meeting was a bit hostile as Kuroka had tried to take Koneko with her, and he would get slightly annoyed by her many attempts of seducing him. Their relationship improved after Kuroka finally accepted that Yoarashi and Koneko were a couple. He'd also has complete trust in his sister-in-law that he even lets Kuroka babysit the children, much to her delight.
Occult Research ClubEdit
Apparently in the past Yoarashi and Vali met, most likely when Yoarashi was performing a job for Azazel. The two sparred a lot and had many fights, through which the two have developed respect for one another. Yoarashi acknowledges that Vali is the strongest Divine Dividing Wielder in history while Vali acknowledges Yoarashi as a strong fighter and even placed him on his list of people he wanted to fight.