Vance's relationship with his younger sister appears to be very close. While separated by 3 years and with different tastes, Vance confides in her his plans (like his crazy attempt to get Robin as a roommate) as well as his horrible roommate situation with Frey. She's also the first to speak up for Vance when their mother tried to push Vance to let her rent out a nicer apartment for him on seeing the horrible dorm room.
Vance's relationship with Frey is very antagonistic. Originally trying to get a hot girl (Robin) for a roommate, the tables got turned on Vance and instead he ended up with Frey. Believing Frey worked for the university, Vance was forced to help out Frey under the pretense it'd keep his records clean of his hacking (not realizing Frey wasn't who he said he was and the school didn't know about his misdeeds). Furthermore, every chance Frey can get, he makes sarcastic remarks to Vance, such as giving Vance's manhood a low rating when he accidentally exposed himself, and twisting his words around so it sounds like Vance is hitting on Frey.
As of right now, there's no actual relationship between Vance and Robin. Who Vance thought he was talking with online was actually Frey. However, Robin appears to detest Vance right now due to his unintended interference with her and Frey's plans to expose government corruption, going as far as asking Frey why he even bothers with Vance in the first place.