Philemon

Who were the three recipients that Paul named in the letter to Philemon? First he named Philemon. The two descriptors Paul used, dear friend and co-laborer, indicate a close relationship with Paul. Either Paul and Philemon spent time together for the Gospel or Paul had detailed information about the letter's recipient and his ministry. Philemon was most likely the head of the house since the discussion regarding Onesimus seems directed to him. But who was Apphia the sister? Was she Philemon's wife, sister, daughter? From Paul's mention of here by name there can be little doubt that her influence in the congregation was noteworthy. And finally Paul names Archippus whom he refers to as a soldier. Was he Philemon's son, Apphia's husband, or some other relative?  I wonder what we can learn from this very brief interaction with Philemon's household?
Stuart