Can a detective be hired from a creditor when the payor of a lease is in default and can that detective contact family members if they were not listed as references on the application?

In most cases, in most places, a detective can be hired for most any reason. The detective must adhere to the local and state laws regarding investigations, however. As part of their job, a detective may speak with anyone and ask questions about another person. This is typically referred to as an interview. The interviewee (the family members) are under no obligation to speak with the detective and can refuse to provide any information at all if they so desire. You (or your friends, family, and any others) are never obligated to provide information to anyone except as required by a court of law. Believe me, you will know when the court requires it because you will most likely be speaking to a judge or a sworn law enforcement officer.