To be clear, parallels are measured according to declination (distance from the celestial equator, not the ecliptic). The one degree orb that is suggested is one degree of declination, not latitude nor longitude. If a planet is at -5.3 declination (negative is South of the equator) and another planet is at -6.1 declination, then the two are loosely within orb for a parallel. If one planet is at -5.3 and another is at 5.2 (North of the equator), then the two are contra-parallel (like an opposition for parallels). I've seen plenty of charts in which two planets are in longitudinal aspect and are parallel at the same time. It should be noted, however, that most aspects do not also involve a parallel. So, to put it short and sweet, aspects are measured by longitude (along the ecliptic) and parallels are measured in declination (distance from the equator).