Okay, it might not necessarily be illegal in the general case, but in the specific case described by the OP, asking that question, getting an answer, and then s

Okay, it might not necessarily be illegal in the general case, but in the specific case described by the OP, asking that question, getting an answer, and then saying "See you later <eom>" makes it clear that that was discrimination in the hiring process based on family responsibilities, no?