The use of the appellation of senior and junior in colonial records merely refers to the elder and younger persons of the same name in the same town. Here’s a great example from Middlesex Court Records, Folio #53:
John Hayward senior aged about 30 yeares of age saith that about the latter end of summer last hee met with Philip Reade [splotch on document] and hee was drunke for he could not speake rationally . . .
John Hayward junior about 29 yeares of age saith the same above written being present with his cosen.
Taken upon oath this 13th day of Aprill 1670 by Daniel Gookin.