Phoebe is the Chief's niece but it is not revealed which of her parents is the Chief's sibling.
Unfortunately her visit comes at the same time that Max is hiding Hymie in his apartment to save him from being disassembled following his unexplained attack on the Chief.
Inevitably, Phoebe runs into Hymie, who Max introduces as his cousin. Not so predictably she falls in love with Hymie, not realising that he is a robot. When Max tries to explain to her why the relationship cannot work she is impressed by Max's kindliness and transfers her affections to Max instead, prompting the Chief to implore her, "If it comes down to a choice between the two of them ... please take Hymie."