Jamieson, Fausset and Brown on Philemon 1:2

2. Apphia--the Latin, "Appia"; either the wife or some close relative of Philemon. She and Archippus, if they had not belonged to his family, would not have been included with Philemon in the address of a letter on a domestic matter.

Archippus--a minister of the Colossian Church (Col 4:17).

fellow soldier--(2Ti 2:3).

church in thy house--In the absence of a regular church building, the houses of particular saints were used for that purpose. Observe Paul's tact in associating with Philemon those associated by kindred or Christian brotherhood with his house, and not going beyond it.