It seems that the so-doshiyori (officers who worked under the town magistrate) system in Imai-cho started in the Keicho era (1596 - 1615) and the Imanishi family and the Ozaki family were originally appointed to that position but, during the Kanei era (1624 - 1644), the Ueda family was added to make up a group of three so-doshiyori with the Imanishi family being at the head of that group.
今井町の惣年寄制は、慶長に始まったようで、初めは今西・尾崎両家が任命されたが、寛永に上田家が加えられて合計三人となり、今西家が筆頭になっている。