What the Celts had to say about themselves had to wait until many generations later when the spread of Christianity had reached to the end of the world. The Irish appear to be the earliest writers. Most of this record was written by priests who were the most educated, and were familiar with biblical and classical writers of the day. The earliest records were law tracts which had to deal with social organization. A tract called "Crith Gablach" deals mostly with various grades of farmer! Social rank was very important often demonstrated by their burial traditions, which included decorated jewelery of gold or bronze. It appears that there were distinct class divisions. [Caesar himself used the term "rex" (king) to describe the leaders.] Under the kings were nobles, then warriors, then the "aes dana" (the smart guys), then the freeman (small farmers and craftsmen), and then the slaves. "Brehon law" was followed under the judges known as "brithem".
Central to this society's organization was the "tuatha" (tuath=tribe, or people, or clan). Each was ruled by a head (ri, or king) who in turn could be "under king" to a greater "ri" called "ri ruirech"... so on and so on, up the line to a provincial king. The under king would give hostages to the higher king in return for protection. This hostage giving was to become a key element in our JONES family, but that is yet to come. Thus the "tauth" was the political unit.
The social unit was the "fine" (kin group). This was an extended family of all males with a great grandfather in common. It would include second cousins and all the female members as well. This family grouping become the "derbfine" (sure kin). The family to five generations was called "ira-fine", and to six generations was called the "indfine". The custom inherited from the Celts was that the "fine" (kin group) was responsible for the actions of its individual members. This Celtic inheritance was to become the foundation for our own Welsh Laws collected by a JONES father-in-law, Hywel Dda!