"Junior" and "Senior" most often refer to relative ages until in the 20th century. They may be applied by records-keepers such as tax assessors or County Clerks, to differentiate same-named persons for official purposes, and may not be utilized by the persons themselves.
As the eldest died, the next in age might be 'promoted' and so forth down the line if there were more than two.
Further documentation of your persons of interest in tax records and court records, estate records and deeds can really help to develop each person as a collection of discrete records that define identity (such as place of residence and neighbors and relatives), even where the persons are related and living close to each other.