Kaneko Takeshi's Links
Rin is Takeshi's older sibling. Although related and eventually in the same gang, Rin almost never interacts with her brother. She can't deal with how sickly he appears and prefers to not associate with him at all.
Nii-chan is Takeshi's older brother. He has always had a soft spot for Takeshi, especially after Takeshi's hardships. Nii-chan has always been a big advocate for Takeshi joining his gang and was the one who suggested Rider be Takeshi's support. Nii-chan makes an active effort to interact with his younger brother, but often doesn't get far due to Takeshi's unsociable nature.
Rider initial purpose was to ensure that Takeshi didn't injure himself when he had his cyberware induced fits. This was to keep Rider busy and also allow Takeshi to be a more functional member of the gang. He obsessively monitored Takeshi's health, quickly imprinting on him. After becoming sentient, Rider's affection for Takeshi grew exponentially to the point where it was no longer out of concern for his health but genuine attraction to the man. After asking the rest of the gang for advice on what to do, Rider has initiated a relationship with Takeshi.